Emission control system with temperature measurement and methods for use therewith

ABSTRACT

Aspects of the subject disclosure may include, for example, an emission control system that includes an emission control device having a plurality of passages to facilitate emission control of an exhaust gas from a vehicle engine. A controller determines a resonant frequency of a coil and generates a control signal to control induction heating of the emission control device based on the resonant frequency of the coil. An alternating current (AC) source responds to the control signal by selectively generating a power signal to the coil to facilitate the induction heating of the emission control device via the coil.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present U.S. Utility Patent Application claims priority pursuant to35 U.S.C. § 120 as a continuation-in-part of U.S. Utility applicationSer. No. 15/819,324, entitled “EMISSION CONTROL SYSTEM WITH FREQUENCYCONTROLLED INDUCTION HEATING AND METHODS FOR USE THEREWITH,” filed Nov.21, 2017, which claims priority pursuant to 35 U.S.C. § 119(e) to U.S.Provisional Application No. 62/426,261, entitled “TUNING INDUCTIONHEATING OF A GASEOUS EMISSIONS TREATMENT APPARATUS,” filed Nov. 24,2016, all of which are hereby incorporated herein by reference in theirentirety and made part of the present U.S. Utility Patent Applicationfor all purposes.

The present U.S. Utility Patent Application also claims prioritypursuant to 35 U.S.C. § 120 as a continuation-in-part of U.S. Utilityapplication Ser. No. 15/495,039, entitled “EMISSION CONTROL SYSTEM WITHINDUCTION HEATING AND METHODS FOR USE THEREWITH”, filed Apr. 24, 2017,which claims priority as a continuation-in-part of U.S. Utilityapplication Ser. No. 14/829,375, entitled “CATALYTIC CONVERTER SYSTEMWITH CONTROL AND METHODS FOR USE THEREWITH”, filed Aug. 18, 2015, issuedas U.S. Pat. No. 9,657,622 on May 23, 2017, which claims prioritypursuant to 35 U.S.C. § 119(e) to U.S. Provisional Application No.62/041,053, entitled “THERMALLY MANAGED CATALYTIC CONVERTER CONTROLPROTOCOL”, filed Aug. 23, 2014, all of which are hereby incorporatedherein by reference in their entirety and made part of the present U.S.Utility Patent Application for all purposes.

U.S. Utility patent application Ser. No. 14/829,375 also claims prioritypursuant to 35 U.S.C. § 120 as a continuation-in-part of U.S. Utilityapplication Ser. No. 14/452,800, entitled “CATALYTIC CONVERTERSTRUCTURES WITH INDUCTION HEATING”, filed Aug. 6, 2014, issued as U.S.Pat. No. 9,488,085 on Nov. 8, 2016, which claims priority pursuant to 35U.S.C. § 119(e) to U.S. Provisional Application No. 61/910,067, entitled“CATALYTIC CONVERTER USING FIELD HEATING OF METAL COMPONENT”, filed Nov.28, 2013, and U.S. Provisional Application No. 61/879,211, entitled“CATALYTIC CONVERTER EMPLOYING ELECTROHYDRODYNAMIC TECHNOLOGY”, filedSep. 18, 2013, all of which are hereby incorporated herein by referencein their entirety and made part of the present U.S. Utility PatentApplication for all purposes.

U.S. Utility patent application Ser. No. 15/495,039 also claims prioritypursuant to 35 U.S.C. § 120 as a continuation-in-part of U.S. Utilityapplication Ser. No. 15/343,533, entitled “EMISSION CONTROL SYSTEM WITHCONTROLLED INDUCTION HEATING AND METHODS FOR USE THEREWITH”, filed Nov.4, 2016, which claims priority pursuant to 35 U.S.C. § 119(e) to U.S.Provisional Application No. 62/258,071, entitled “CATALYTIC CONVERTERSYSTEM WITH CONTROLLED INDUCTION HEATING AND METHODS FOR USE THEREWITH”,filed Nov. 20, 2015, all of which are hereby incorporated herein byreference in their entirety and made part of the present U.S. UtilityPatent Application for all purposes.

FIELD OF THE DISCLOSURE

This disclosure relates to a structures and methods of operation ofemission control systems for treating vehicle exhaust gases.

BACKGROUND

The U.S. Department of Transportation (DOT) and the U.S. EnvironmentalProtection Agency (EPA) have established U.S. federal rules that setnational greenhouse gas emission standards. Beginning with 2012 modelyear vehicles, automobile manufacturers required that fleet-widegreenhouse gas emissions be reduced by approximately five percent everyyear. Included in the requirements, for example, the new standardsdecreed that new passenger cars, light-duty trucks, and medium-dutypassenger vehicles had to have an estimated combined average emissionslevel no greater than 250 grams of carbon dioxide (CO₂) per mile invehicle model year 2016.

Catalytic converters are used in internal combustion engines to reducenoxious exhaust emissions arising when fuel is burned as part of thecombustion cycle. Significant among such emissions are carbon monoxideand nitric oxide. These gases are dangerous to health but can beconverted to less noxious gases by oxidation respectively to carbondioxide and nitrogen/oxygen. Other noxious gaseous emission products,including unburned hydrocarbons, can also be converted either byoxidation or reduction to less noxious forms. The conversion processescan be effected or accelerated if they are performed at high temperatureand in the presence of a suitable catalyst being matched to theparticular noxious emission gas that is to be processed and converted toa benign gaseous form. For example, typical catalysts for the conversionof carbon monoxide to carbon dioxide are finely divided platinum andpalladium, while a typical catalyst for the conversion of nitric oxideto nitrogen and oxygen is finely divided rhodium.

Catalytic converters have low efficiency when cold, i.e. the runningtemperature from ambient air start-up temperature to a temperature ofthe order of 300 C or “light-off” temperature, being the temperaturewhere the metal catalyst starts to accelerate the pollutant conversionprocesses previously described. Below light-off temperature, little tono catalytic action takes place. This is therefore the period during avehicle's daily use during which most of the vehicle's pollutingemissions are produced.

BRIEF DESCRIPTION OF THE DRAWINGS

For simplicity and clarity of illustration, elements illustrated in theaccompanying figure are not drawn to common scale. For example, thedimensions of some of the elements are exaggerated relative to otherelements for clarity. Advantages, features and characteristics of thepresent disclosure, as well as methods, operation and functions ofrelated elements of structure, and the combinations of parts andeconomies of manufacture, will become apparent upon consideration of thefollowing description and claims with reference to the accompanyingdrawings, all of which form a part of the specification, wherein likereference numerals designate corresponding parts in the various figures,and wherein:

FIG. 1 is a perspective outline view of a catalytic converter brickbeing formed in an extrusion process.

FIG. 2 is a longitudinal sectional view of a known form of catalyticconverter.

FIG. 3 is a longitudinal sectional view of a catalytic converterassembly according to an embodiment of the disclosure.

FIG. 4 is a cross-sectional view of a catalytic converter according toanother embodiment of the disclosure.

FIG. 5 is a cross-sectional view of a fragment of a catalytic convertersubstrate according to an embodiment of the disclosure.

FIG. 6 is a longitudinal sectional view of the substrate fragmentillustrated in FIG. 5 taken on the line B-B of FIG. 5.

FIG. 7 is a perspective end view of a larger fragment corresponding tothe small substrate fragment shown in FIGS. 5 and 6.

FIG. 8 is a perspective end view similar to FIG. 7 but showing acatalytic converter substrate according to another embodiment of thedisclosure.

FIG. 9 is a side view of a wire insert for use in a catalytic convertersubstrate of the form shown in FIG. 8.

FIG. 10 is a longitudinal sectional view of a fragment of a catalyticconverter substrate showing the wire insert of FIG. 9 inserted into thesubstrate.

FIG. 11 is a longitudinal sectional view of a fragment of a catalyticconverter substrate showing an inserted wire insert according to anotherembodiment of the disclosure.

FIG. 12 is a cross-sectional view of a fragment of a catalytic convertersubstrate according to a further embodiment of the disclosure.

FIG. 13 is a longitudinal sectional view of the substrate fragmentillustrated in FIG. 12.

FIG. 14 is a perspective end view of a fragment of a catalytic convertersubstrate and emitter and collector electrodes illustrating anembodiment of the disclosure.

FIG. 15 is a perspective end view of a fragment of a catalytic convertersubstrate and emitter and collector electrodes illustrating analternative embodiment of the disclosure.

FIG. 16 is a perspective end view of a fragment of a catalytic convertersubstrate and collector electrode illustrating a further embodiment ofthe disclosure.

FIG. 17 is a perspective end view of fragments of a catalytic convertersubstrate and emitter electrode and, to a larger scale, a collectorelectrode, illustrating another embodiment of the disclosure.

FIG. 18 is a schematic view of a catalytic converter system according toan embodiment of the disclosure.

FIG. 19 is a block diagram representation of a feedback control loopaccording to an embodiment of the disclosure.

FIG. 20 presents graphical representations of a control signal andcatalytic converter temperature according to an embodiment of thedisclosure.

FIG. 21 is a block diagram representation of a controller according toan embodiment of the disclosure.

FIG. 22 is a flow diagram representation of a method according to anembodiment of the disclosure.

FIG. 23 is a block diagram representation of an electromagnetic fieldgenerator 300 according to an embodiment of the disclosure.

FIG. 24 is a block diagram representation of an electromagnetic fieldgenerator 300 according to an embodiment of the disclosure.

FIG. 25 is a graphical diagram of a control set point as a function oftime according to an embodiment of the disclosure.

FIG. 26 is a graphical diagram of a power signal as a function of timeaccording to an embodiment of the disclosure.

FIG. 27 is a flow diagram of a method according to an embodiment of thedisclosure.

FIG. 28 is a flow diagram of a method according to an embodiment of thedisclosure.

FIG. 29 is a flow diagram of a method according to an embodiment of thedisclosure.

FIG. 30 is a graphical diagram of a temperature hysteresis curveaccording to an embodiment of the disclosure.

FIG. 31 is a flow diagram of a method according to an embodiment of thedisclosure.

FIG. 32 is a graphical diagram of a temperature, inductance andresonance characteristic according to an embodiment of the disclosure.

DETAILED DESCRIPTION

A catalytic converter may take any of a number of forms. Typical ofthese is a converter having a cylindrical substrate of ceramic material,generally called a brick, an example of which is shown in FIG. 1. Thebrick 10 has a honeycomb structure in which a number of small areapassages or cells 14 extend the length of the brick, the passages beingseparated by walls 16. There are typically from 400 to 900 cells persquare inch of cross-sectional area of the substrate unit and the wallsare typically in the range 0.006 to 0.008 inches in thickness. Asindicated in FIG. 1, the ceramic substrates can be formed in anextrusion process in which green ceramic material is extruded through anappropriately shaped die and units are cut successively from theextrusion, the units being then cut into bricks which are shorter than aunit. The areal shape of the passages or cells 12 may be whatever isconvenient for contributing to the overall strength of the brick whilepresenting a large contact area at which flowing exhaust gases caninteract with a hot catalyst coating the interior cell walls.

The interiors of the tubular passages in the bricks can be wash-coatedwith a layer containing the particular catalyst material. These tubularpassages can have a circular or elliptical cross-section, a rectangular,square or other polygonal cross section or other cross section. Asuitable wash-coat can contain a base material, suitable for ensuringadherence to the cured ceramic material of the substrate, and entrainedcatalyst material for promoting specific pollution-reducing chemicalreactions. Examples of such catalyst materials are platinum andpalladium which are catalysts effective in converting carbon monoxideand oxygen to carbon dioxide, and rhodium which is a catalyst suitablefor converting nitric oxide to nitrogen and oxygen, however othercatalysts can also be employed to promote high temperature oxidation orreduction of other gaseous materials. The wash-coating can be preparedby generating a suspension of the finely divided catalyst in a ceramicpaste or slurry, the ceramic slurry serving to cause the wash-coat layerto adhere to the walls of the ceramic substrate. As an alternative towash-coating to place catalyst materials on the substrate surfaces, thesubstrate material itself may contain a catalyst assembly so that theextrusion presents catalyst material at the internal surfaces boundingthe substrate passages or cells.

A catalytic converter may have a series of such bricks, each having adifferent catalyst layer depending on the particular noxious emission tobe neutralized. Catalytic converter bricks may be made of materialsother than fired ceramic, such as stainless steel. Also, they may havedifferent forms of honeycombed passages than those described above. Forexample, substrate cells can be round, square, hexagonal, triangular orother convenient section. In addition, if desired for optimizingstrength and low thermal capacity or for other purposes, some of theextruded honeycomb walls can be formed so as to be thicker than other ofthe walls, or formed so that there is some variety in the shape and sizeof honeycomb cells. Junctions between adjacent interior cell walls canbe sharp angled or can present curved profiles.

Typically, as shown in FIG. 2, the brick 10 is a wash-coated ceramichoneycomb brick wrapped in a ceramic fibrous expansion blanket 16. Astamped metal casing or can 18 transitions between the parts of theexhaust pipe fore and aft of the catalytic converter so as to encompassthe blanket wrapped brick. The casing 18 is typically made up of twoparts which are welded to seal the brick in place. The expansion blanketprovides a buffer between the casing and the brick to accommodate theirdissimilar thermal expansion coefficients. The sheet metal casingexpands many times more than the ceramic at a given temperature increaseand if the two materials were bonded together or in direct contact witheach other, destructive stresses would be experienced at the interfaceof the two materials. The blanket also dampens vibrations from theexhaust system that might otherwise damage the brittle ceramic.

In use, the encased bricks are mounted in the vehicle exhaust line toreceive exhaust gases from the engine and to pass them to the vehicletail pipe. The passage of exhaust gases through the catalytic converterheats the brick to promote catalyst activated processes where theflowing gases contact the catalyst layer. Especially when the vehicleengine is being run at optimal operating temperature and when there canbe substantial throughput of exhaust gases, such converters operatesubstantially to reduce the presence of noxious gaseous emissionsentering the atmosphere. Such converters have shortcomings however atstart-up when the interior of the brick is not at high temperature andduring idling which may occur frequently during city driving or whenwaiting for a coffee at a Tim Hortons drive-through.

Converter shape, profile and cell densities vary among differentmanufacturers. For example, some converter bricks are round and some areoval. Some converter assemblies have single stage bricks that aregenerally heavily wash-coated with the catalyst metals, while others mayhave two or three converter bricks with different wash-coatings on eachbrick. Some exhausts have 900, 600 and 400 cell per square inch (cpsi)cell densities used in the full exhaust assembly, while others use only400 cpsi bricks throughout. A close-coupled converter may be mounted upclose to the exhaust manifold with a view to reducing the period betweenstart-up and light-off. An underfloor converter can be located furtherfrom the engine where it will take relatively longer to heat up but berelatively larger and used to treat the majority of gases once theexhaust assembly is up to temperature. In another configuration, a unitfor reducing the period to light-off and a unit to deal with high gasflow after light-off are mounted together in a common casing.

At one or more locations in the converter assembly, sensors are mountedin the exhaust gas flow provides feedback to the engine control systemfor emission checking and tuning purposes. Aside from start-up, controlof fuel and air input has the objective typically of maintaining adesired air:fuel ratio, for example a 14.6:1 air:fuel ratio or otherair:fuel ratio for an optimal combination of power and cleanliness. Aratio higher than this produces a lean condition—not enough fuel. Alower ratio produces a rich condition—too much fuel. The start-upprocedure on some vehicles runs rich for an initial few seconds to getheat into the engine and ultimately the catalytic converter. Thestructures and operating methods described below for indirectly heatingthe catalyst layers and the exhaust gases can be used with each of aclose-coupled catalytic converter, an underfloor converter, and acombination of the two.

FIG. 3 shows an assembly having two bricks of the sort illustrated inFIGS. 1 and 2, but in which one brick can be modified to enableinduction heating. Induction heating is a process in which a metal bodyis heated by applying a varying electromagnetic field so as to changethe magnetic field to which the metal body is subject. This, in turn,induces eddy currents within the body, thereby causing resistive heatingof the body. In the case of a ferrous metal body, heat can also begenerated by a hysteresis effect. When non-magnetized ferrous metal isplaced into a magnetic field, the metal becomes magnetized with thecreation of magnetic domains having opposite poles. The varying fieldperiodically initiates pole reversal in the magnetic domains, thereversals in response to high frequency induction field variation on theorder of 1,000s to 1,000,000s cycles per second (Hz) depending on thematerial, mass, and shape of the ferrous metal body. Magnetic domainpolarity is not easily reversed and the resistance to reversal, calledmagnetic hysteresis, causes further heat generation in the metal.

As illustrated in FIG. 4, surrounding the ceramic substrate is a metalcoil 20 and, although not shown in the figure, located at selectedpositions within the ceramic substrate 10 are metal elements which maytake any of a number of forms. By generating a varying electromagneticfield at the coil 20, a chain reaction can be initiated, the end resultof which is that after start-up of a vehicle equipped with an exhaustsystem embodying the disclosure, light-off may be attained more quicklyin the presence of the varying electromagnetic induction field than ifthere were no such field. The chain reaction can be as follows: thevarying electromagnetic field induces eddy currents in the metalelements; the eddy currents cause heating of the metal elements; heatfrom the metal elements is transferred to the ceramic substrate 10; heatfrom the heated substrate is transferred to exhaust gas as it passesthrough the converter; and the heated exhaust gas causes the catalyticreactions to take place more quickly compared to unheated exhaust gas.

The coil 20 can be a wound length of copper tube, although othermaterials such as copper or litz wire, or other conductors such asaluminum, steel, etc. may be used. Copper tube can be offer high surfacearea in terms of other dimensions of the coil; induction being askin-effect phenomenon, high surface area is of advantage in generatingthe varying field. If litz wire or copper wire is used, an enamel orother coating on the wire can be configured not to burn off duringsustained high input current and high temperature operation of theconverter.

A layer of 22 of electromagnetic field shielding material such asferrite can be located immediately outside the coil 20 to provide aninduction shielding layer and reduces induction loss to the casing 18.The ferrite shield 22 also acts to increase inductive coupling to theceramic substrate 10 to focus heating.

The coil can be encased in cast and cured dielectric or insulation. Thecast dielectric or insulation functions both to stabilize the coilposition and to create an air-tight seal to confine passage of theexhaust gases through the brick 10 where the catalytic action takesplace. The insulation also provides a barrier to prevent the coil 20from shorting on the casing 18 or the ferrite shield 22. The insulationcan be a suitable alumino-silicate mastic. In an alternative embodiment,the converter is wrapped in an alumino-silicate fibre paper. In onemanufacturing method, a copper coil 20 is wrapped around the ceramicsubstrate 10 and then placed in the casing 18. In an alternativemanufacturing method, the coil 20 is placed in the casing 18 and theceramic substrate 10 is inserted into the coil can assembly.

In one embodiment of the disclosure, a varying electromagnetic inductionfield is generated at the coil by applying power from either a DC or ACsource. Conventional automobiles have 12 VDC electrical systems. Theinduction system can operate on either DC or AC power supply. Theinduction signal produced can also be either DC or AC driven. For eitherDC or AC, this produces a frequency of 1 to 200 kHz or higher, a RMSvoltage 130V to 200V and amperage of 5 to 8 A using 1 kw of power as anexample. In one example suitable for road vehicles, a DC to DC converterconverts the vehicle's 12 VDC battery power to the required DC voltageoutlined above. In another example suitable for conventional roadvehicles, a DC to AC inverter converts the vehicle's 12V DC batterypower to the desired AC voltage outlined above.

Another example is more suited to hybrid vehicles having both internalcombustion engines and electric motors with on-board batteries rated inthe order of 360V and 50 kW of power. In this case, the battery supplypower is higher, but the same basic DC to DC bus or DC to AC inverterelectrical configuration can be applied. An IGBT high speed switch canbe used to change the direction of electrical flow through the coil. Interms of the effect of a varying electromagnetic induction field onmetal in the ceramic substrate, a low switching frequency produces alonger waveform providing good field penetration below the surface ofthe metal element and therefore relatively uniform heating. However,this is at the sacrifice of high temperature and rapid heating owing tothe lack of switching. In contrast, a high switching frequency producesa shorter waveform, which generates higher surface temperature at thesacrifice of penetration depth. Applied power is limited to avoid therisk of melting the metal elements. A suitable power input to a singlebrick coil can be of the order of 1.1 kw.

As previously described, metal elements are located at selectedlocations of the ceramic substrate 10. For two identical metal elements,generally, a metal element closer to the source of the induction fieldbecomes hotter than an equivalent metal element located further awayfrom the source because there is an increase in efficiency; i.e. thelevel of induction achieved for a given power input. With a regularinduction coil 10 as illustrated, metal elements at the outside of thebrick 10 are near to the coil 20 and become very hot, while anequivalent metal element near the substrate center remains relativelycool. An air gap 26 between the coil 20 and the nearest inductance metalelements prevents significant heat transfer from the inductance metalelements to the coil which would otherwise increase the coil resistivityand so lower its efficiency. In an alternative embodiment, a relativelyhigher concentration of the metal elements can be sited towards thecenter of the ceramic substrate to compensate for the fact that thefield effect from the coil source can be considerably less near thecentre of the substrate than near the outer part of the substrate. In afurther embodiment, a relatively higher metal element load can belocated at some intermediate position between the centre and perimeterof the ceramic substrate, whereby heat generated within the intermediatelayer flows both inwardly to the center and outwardly to the perimeterfor more efficient overall heating. The coil 20 can be sized to themetal load to achieve high efficiency in terms of generating heat and interms of speed to light-off.

The electromagnetic induction field can be tuned to modify heatingeffects by appropriate selection of any or all of (a) the electricalinput waveform to the coil, (b) nature and position of passive fluxcontrol elements, and (c) nature, position, and configuration of thecoil 20. For example, the induction field can be tuned to the locationof metal elements or to the location of high concentration of suchelements in the ceramic substrate 10. Alternatively, or in addition, theapplied field can be changed with time so that there is interdependencebetween the induction field pattern and the particular operational phasefrom pre-start-up to highway driving. In an alternative configuration,more than one coil can be used to obtain desired induction effects. Forexample, as shown in the cross sectional view of FIG. 4, the ceramicsubstrate 10 has an annular cross-section with a first energizing coil20 at the substrate perimeter and a second energizing coil at thesubstrate core.

As shown in the fragmentary sectional views of FIGS. 5 and 6, in oneembodiment of the disclosure, the metal elements are metal particles 28which are embedded in the walls 14 of the ceramic honeycomb substrate,the particle size being less than the width of walls 14. As part of themanufacturing process, the metal particles are added and mixed with aceramic base material while the ceramic is still green or flowable; i.e.before it is extruded. In this way, the particles are distributedrelatively evenly throughout the ceramic base material to be extruded.In operation of this embodiment, when a varying electromagneticinduction field is applied from the coil 20, the ceramic material in thesubstrate is comparatively invisible to the applied field and thereforedoes not heat up. The metal particles 28 heat up and conduct heat to thewalls 14 of the ceramic honeycomb within which they are bound.

In an alternative manufacturing embodiment, mixing of the ceramic basematerial with metal particles and subsequent extrusion of the mixture toform the honeycomb substrate are configured so that selected locationsin the substrate have a greater metal particle concentration than otherlocations. Such a configuration may be attained by bringing together atthe extruder several streams of green ceramic material, with the streamshaving different levels of metal content from one another. The streamsare then fused immediately before extrusion so that the variation inmetal content is mirrored across the cross-section of the extrudedsubstrate. In a further embodiment, metal particles are used that areelongate or otherwise asymmetric so that they tend to align somewhatcloser to converter cell walls in the course of the extrusion process.In another embodiment, the particle lengths are made sufficiently longthat at least some adjacent particles come into electrical contact witheach other in the course of mixing or subsequent extrusion.

In alternative embodiments of the disclosure, the metal elements arelocated within the ceramic honeycomb structure, but not embedded withinthe material of the honeycomb structure itself. For example, duringpost-processing of ceramic substrate bricks, metal elements arepositioned in selected cells 12 of the substrate or brick 10. In oneimplementation as illustrated in FIG. 7, a high concentration of metalparticles is mixed with a mastic and the resulting mixture is injectedusing a method such as that described in copending utility patentapplication Ser. No. 13/971,129 (A catalytic converter assembly andprocess for its manufacture), filed Aug. 20, 2013, the disclosure ofwhich application is incorporated herein by reference in its entiretyand made part of the present application for all purposes. Followinginjection, injected threads 30 of the mastic mixture is cured by, forexample, microwave heating as described in copending utility patentapplication Ser. No. 13/971,247 (A catalytic converter assembly andprocess for its manufacture) filed Aug. 20, 2013, the disclosure ofwhich application is also incorporated herein by reference in itsentirety and made part of the present application for all purposes. Inone implementation, the mastic base material is a low viscosity,paste-like mixture of glass fibers, clay slurry, polymer binder andwater, from which the water and the organic binder are driven off in thecourse of the curing process. Following curing, the injected threads 30are predominantly silica in a porous matrix of silica, ceramic and metalparticles.

In another exemplary configuration (not shown), selection of passages incell 12 to be injected can be made so that the threads of cured masticmetal mixture are not uniformly distributed, but generally occupy anintermediate annular zone of the cylindrical substrate. In the operationof such a structure, heat is preferentially generated at the annularzone and is transferred from the zone sites inwardly towards thesubstrate core and outwardly towards its perimeter. Metal particleswithin the mastic metal mixture injected into a cell can bepredominantly situated close to the cell interior surface rather thantowards the cell center so as to localize heat generation near the cellsurfaces and to get greater heat transfer and speed of such transfer tothe ceramic substrate. Appropriately directed agitation of the loadedconverter brick after during and/or after extrusion and before curingcan encourage some migration of metal particles towards the cell walls.

In injected cell implementations, any cell which is fully blocked with athread of the mastic and metal particles cannot function to catalyze apollution-reducing reaction as exhaust gas passes through the cell. Sucha plugged cell is used solely for heating at start-up or when idling.Consequently, only selected ones of the cells are filled with thecomposite heating material. In the example illustrated, the substratehas 400 cells per square inch. Of these, from 8 to 40 cells per squareinch are filled with the metal mastic composite depending on the radialposition of the cells and such that over the full areal extent of thesubstrate, the blocked cells occupy from 2 to 10% of the substrate area.

In a further embodiment of the disclosure, discrete metal elements thatare larger than the particle sizes discussed with the FIG. 7 embodimentare inserted at selected cell locations in the catalytic convertersubstrate. As shown in FIG. 8, exemplary metal elements are wires 32which are positioned within selected substrate cells and which extendalong the full length of the cells from the brick entrance to its exit.The inserted wires 32 may, for example, be of round, square or othersuitable cross-section and may be constructed using copper, steel,aluminum, stainless steel or other metal or ferromagnetic elementshaving desirable electromagnetic properties that promote inductionheating. As shown in the FIG. 8 embodiment, the ceramic convertersubstrate 10 has square cells and round section wires. Square sectionwires provide better heat transfer to the square section cells due tohigh contact area between the two materials. However, round sectionwires are easier to insert into the square section cells owing to therebeing less surface area contact causing insertion resistance. The wiresmay be fixed into their respective cells by a friction fit which is atleast partially achieved by closely matching the wire exterior areadimensions to the cell area dimensions so that surface roughness of thewire surface and the cell walls locks the wires in place. Wire is drawnto be from 0.002 inches to 0.005 inches less in width than the cellwidth to enable insertion.

In one configuration, an insert 34 is formed of wire to have a bow-shapeas shown in FIGS. 9 and 10. The bowed wire 34 has memory so that afterthe bow is straightened as the wire is inserted into a cell 12, theinsert 34 tends to return to its bow shape causing center and endregions of the wire to bear against opposed sides or corners of the cell12 and so enhance the friction fit to retain the wire in place in thecell. Alternatively, or in addition, wires 36 are crimped at their endsas shown in the embodiment of FIG. 11 so as to establish end bearingcontact sites. The overall friction fit in each case is such as toresist gravity, vibration, temperature cycling, and pressure on thewires as exhaust gases pass through the converter.

Wires may alternatively, or in addition, be fixed into the cells bybonding outer surfaces of the wires to interior surfaces of respectivecells. In exemplary bonding processes, the wire is at least partiallycoated with an adhesive/mastic before insertion, or a small amount ofadhesive/mastic is coated onto the cell interior walls before wireinsertion. High temperature mastic materials and composite adhesives areused. Suitable mastic, for example, is of the same form as that used inthe injection embodiments previously described. A composite adhesive,for example, is a blend of ceramic and metal powders with a bindertransitioning between the two main materials. Such a blend is used tominimize temperature cycling stress effects in which there may besignificant metal wire expansion/contraction, but vanishingly smallexpansion/contraction of the ceramic substrate. This differential canproduce stresses at the adhesive interface between the two materials. Byusing such a composite adhesive, movement of a bonded wire relative tothe surrounding cell surface is minimized and heat transfer increasedheat transfer is obtained by the presence of the composite adhesivematerial.

As shown in the embodiment of FIG. 8, an array of wires having a uniformdistribution through the array of converter cells is used. In oneexample, 1 wire is inserted for every 25 cells of a 400 cpsi substrate.This has a satisfactory heating performance and not too great anocclusion of converter cells from the viewpoint of pollution-cleaningcatalytic reactions implemented at the converter. A significantly higherratio of wires to cells can result in slower heating to light-offbecause of the high overall thermal capacity represented, in total, bythe wires and because of the fact that some wires block the “line ofsight” field effect on other wires. In contrast, while a significantlylower ratio of wires to cells results in fewer occlusions of convertercells, a sparse distribution of metal of the order of less than 1 wireinserted for every 49 cells in a 400 cpsi substrate results in reducedheat generation and increased time to light-off. As in the case of theinjected metal particle embodiments described previously, wires can beinserted in a non-uniform pattern: for example, to a generally annularconcentration of wire insertions at an intermediate radial positionwithin the ceramic converter substrate; or to position a greaterconcentration of wires near the core of the converter furthest from thecoil compared to the concentration of wires near the perimeter of theconverter.

There are advantages and disadvantages as between using metal particlesand larger metal elements such as wire inserts. Induction heatingproduces a “skin-effect” hot surface of the metal being heated. This canpromote heating efficiency depending on the surface area of the metalelement. Generally, the more surface area there is, the quicker themetal heats-up. However, induction is a line-of-sight process where thesurface that “sees” the inductive field is the one that heats-up firstand gets hotter. Powder particles heat-up quickly and larger bodiesheat-up more slowly. In the case of particles, whether dispersed andembedded in the ceramic substrate material itself or in mastic injectedinto selected cells, each particle acts independently of the next sothere is little conduction between neighboring particles. Consequently,heat distribution may be relatively poor. Larger metal bodies conductheat well throughout their bulk and can operate more efficiently interms of distributing heat. The thin wire embodiments of FIG. 8 canoffer a good compromise between particles and solid bodies in terms ofsurface area, line-of-sight positioning and conduction characteristicsall of which significantly affect the heating performance.

Conduction is the primary source of heat transfer to the ceramicsubstrate and therefore to the exhaust gases when the converter is inoperation. In the case of the wire insert embodiments, there is also asmall amount of convective heat transfer but this is limited as there isonly a small air gap between the wires and the interior surface of thecells so air movement is minimized. There is also a relatively smallamount of radiated heat transfer in the case such as inserted wireswhere the wires are separated over a large part of their surface areafrom the interior of the cells but where the separation is not occluded.

As previously described and illustrated, the distribution of inductancemetal elements relative to the position of cells can be configured sothat the heating effect is generally uniform across the area of theconverter. Especially for start-up and idling, where non-uniform exhaustgas flow patterns may develop, there may be advantage in deliberatelydeveloping a heat pattern across the converter which is not uniform. Aspreviously noted, this may be achieved by appropriately sitinginductance metal elements in selected cells. It may also be achieved inanother embodiment of the disclosure by using differently sized orshaped metal inserts or by using different concentrations of particlesin the injection embodiments. It may be achieved in a furtheralternative structure and method by generating a non-radiallysymmetrical field or generating two or more interfering fields. Suchinduction fields and their interaction could, for example, be varied inthe period from start-up to light-off. Changing heating effects may alsobe achieved using a combination of such inductance metal siting andfield manipulation. Targeted heating that varies in position, time, orboth can be implemented with a view to increasing conversion ofpollutants, to saving power, or for other reasons.

In another embodiment of the disclosure, the metal elements are notentrained within the material of the ceramic substrate and are notinjected or positioned into selected cells. Instead, as shown in thefragmentary section views of FIGS. 12 and 13, a ferrous metal coating 40is formed on the interior surfaces of walls 14 of selected convertercells before application of the catalyst(s) coating 38. Alternatively,(not shown) the ferrous metal coating is laid down as a common coatingwith the catalyst metal(s), either by using alloy particles that containboth the ferrous metal and the catalyst metal(s) or by having a wash inwhich both the ferrous metal particles and the catalyst metal particlesare dispersed. In the latter arrangements, there may be some loss ofcatalyst action arising from the ferrous metal taking some of thecatalyst metal sites and so a compromise is necessary.

All metals are responsive to some extent to an induction field, withferrous metals being the materials most readily heated by such a field.Catalyst materials contained within a wash coat applied to a honeycombsubstrate cell interior are typically platinum group metals—platinum,palladium and rhodium. Such materials have a low magnetic permeabilityof the order of 1×10⁻⁶ (in the case of platinum) and so are influencedonly very slightly by an applied induction field. Moreover, catalystmetals are present in very tiny amounts of the order of a gram perconverter brick so there is insufficient metal in the catalyst assemblyto generate and transfer any noticeable heat to the ceramic substrate instart-up period or idling periods. In contrast, ferrous metals used forthe induction heating are present in an amount of the order of 60 to 200grams per brick and have magnetic permeability of the order of 2.5×10⁻¹in the case of iron.

As previously indicated, induction heating is applied in the periodbefore light-off in order to reduce the amount of harmful pollutantswhich are emitted before the catalyst coatings have reached atemperature at which they start to catalyze reactions in which thepollutants are converted to more benign emissions. Particularly for citydriving, engine operation is frequently characterized by bursts ofacceleration and braking punctuated by periods of idling. At such times,the temperature of the exhaust gas entering the converter and the wallsof the substrate with which the flowing exhaust gas is in contact maystart to fall. If the idling and the cooling continue, the temperatureof the substrate and the gas fall below that required for thepollutant-reducing catalytic reactions to occur. In such periods,heating of the converter substrate is obtained by switching on theinduction heating. At a future point, when the vehicle is no longeridling and the exhaust gas temperature increases past the temperaturerequired for effective catalytic reaction to convert the toxic exhaustgas pollutants to relatively benign products, the induction heating isswitched off.

Embodiments of the induction heating disclosure have been described inthe context of ferrous alloys such as steel which are commerciallyavailable in common shapes and sizes, and at reasonable cost.Alternative ferromagnetic metals such as cobalt or nickel or theiralloys may also be used. The metal used must survive high temperaturereached by the catalytic converter and repeated temperature cycling asthe metal intrusions move repeatedly from a cold start to operatingtemperature and back again. Generally, alloying of iron or otherferromagnetic metal gives advantageous mechanical and physicalproperties such as corrosion/oxidation resistance, high temperaturestability, elastic deformation, and formability.

Referring to FIGS. 14 to 17, embodiments of the disclosure areillustrated which are adapted for electrohydrodynamic (EHD) heat andmass transfer of exhaust gas passing through the passages or cells of acatalytic converter substrate. In the EHD process, free electrons aregenerated and caused to migrate from a charged upstream emitter to agrounded downstream collector 44. In the course of their migration,electrons collide with molecules in the exhaust gas, transferringmomentum to the gas molecules and causing turbulence in the gas flow.This means that there is a lesser tendency for the gas flow through thecells to adopt a laminar flow and/or there is a tendency for a laminargas flow to depart from laminarity. Both tendencies bring more exhaustgas into contact with the walls of the converter substrate cell wallsthan would be the case without EHD stimulation. This results in both anincrease in heat transfer between the exhaust gas and the walls of thesubstrate and an increase in the catalytic pollution-reducing reactionsowing to increased contact of the exhaust gas with hot catalyst at theinterior surfaces of the substrate cell walls.

In operation, in the period between start-up and light-off, thesubstrate walls are at a lower temperature than the exhaust gas. Moreheat is transferred from the flowing exhaust gas to the substrate bystimulation of EHD heat transfer stimulation and the substratetemperature increases at a faster rate than would be the case withoutthe EHD heating process. A control circuit includes a first temperaturesensor to monitor the temperature of the converter substrate and asecond temperature sensor to monitor the temperature of the exhaust gasimmediately upstream of the converter. The control circuit includes acomparator for measuring the difference between the exhaust gas and theconverter substrate temperatures and a switch controlled by thecomparator to switch on EHD voltage to the emitter. Greater speed tolight-off is obtained by switching in the EHD heat transfer process tostimulate heat transfer from the exhaust gas during the start-up tolight-off period. At a future point, when the substrate is sufficientlyhot to cause the pollution reducing catalytic reaction to occur, EHDheat transfer stimulation is switched off.

In addition, during idling periods, the temperature of the exhaust gasentering the converter may start to drop and a situation may arise wherethe catalytic converter substrate walls are still at an optimaltemperature for catalyst reactions, but the gas entering the converteris below a temperature that it is optimal for such reactions. During theidling phases, the converter may remain at or near an optimal operatingtemperature from the viewpoint of reducing harmful emissions, even asthe gas flowing through the converter is cooling down. In such periods,low power heating of the cooling exhaust gas is obtained by switching inthe EHD heat transfer process to draw heat for a limited period of time.At a future point, when the vehicle is no longer idling and the exhaustgas temperature increases past the monitored substrate temperature, theEHD heat transfer stimulation can be switched off.

Referring in detail to FIG. 14, for operating a catalytic converter inwhich EHD is implemented, an emitter 42 is connected to a 25 to 50kilovolts power source delivering very low amperage, the systemtherefore consuming only a few watts and a collector 44 is grounded. Theflow of electrons produces preferential heat exchange between thecharged exhaust gas and the converter substrate compared with thepassage through the catalytic converter of uncharged exhaust gas. Theconductivity of the exhaust gas influences the extent of mixing and flowchanges that, in turn, cause more rapid heat transfer between theconverter substrate and the exhaust gas. Generally, the more conductivethe exhaust gas, the higher the turbulent effect and the greater the EHDheat transfer effect.

As shown in the FIG. 14 embodiment, in a first emitter collectorarrangement, the emitter 42 is a regular mesh of 0.25 inch diameter rodsand 0.375 inch apertures, the mesh mounted immediately upstream of thebrick 10. A collector 44 is a similar metal mesh located immediatelydownstream of the converter brick, this mesh being connected to ground.Interconnection of the upstream mesh to a positive voltage source andinterconnection of the downstream mesh to ground provides the positive(emitter) and negative (collector) electrodes required to generateelectron flow.

As shown in FIG. 15, in a second emitter collector arrangement, aconfiguration of wire inserts is used similar to that shown in FIG. 8except that the wire inserts are interconnected to each other and toground. In the illustrated configuration, a continuous wire 46 is usedand is looped in and out of substrate cells so that adjacent wireinserts are effectively stitched into place.

In another embodiment, as shown in FIG. 16, the mesh collector 44 hasprotruding wires 48 that are aligned with the longitudinal axis ofselected substrate cells. In the course of manufacture, the protrudingwires 48 of the collector 44 are slid back towards the front end of theconverter brick and into the aligned cells 12. The mesh collector islocked to the back side of the substrate. In one form, the protrudingwires 48 have a friction fit within the selected cells 12 as previouslydescribed with reference to FIGS. 8 to 11 or are secured in place usinga suitable adhesive. In another form and associated method, theprotruding wires are pre-located in the selected cells and then bound inplace by injecting a metal mastic matrix into the cell and then dryingand sintering the matrix.

In a further emitter collector arrangement as shown in FIG. 17, theemitter 42 is a metal sphere or disc having a diameter matching thediameter of a cylindrical converter substrate, the sphere being devoidof angular corners so that electron emission is relatively evenlydistributed across its surface. A series of collectors are formed byfilling selected converter cells 12 with a metal powder in a bindermatrix to constitute a series of collector sites, the collector threads30 within the plugged cells being connected together and to ground by,for example, a mesh of the form shown in FIG. 16 but with relativelyshorter contact projections 48. The metal particles are mixed with amastic and the resulting mixture is injected using a method such as thatdescribed in copending utility patent application Ser. No. 13/971,129 (Acatalytic converter assembly and process for its manufacture), filedAug. 20, 2013, the disclosure of which application is incorporatedherein by reference in its entirety and made part of the presentapplication for all purposes. Following injection, injected threads 30of the mastic mixture are cured by, for example, microwave heating asdescribed in copending utility patent application Ser. No. 13/971,247 (Acatalytic converter assembly and process for its manufacture) filed Aug.20, 2013, the disclosure of which application is also incorporatedherein by reference in its entirety and made part of the presentapplication for all purposes. In one implementation, the mastic basematerial is a low viscosity, paste-like mixture of glass fibers, clayslurry, polymer binder and water, from which the water and the organicbinder are driven off in the course of the curing process. Followingcuring, the injected threads 30 are predominantly silica in a porousmatrix of silica, ceramic and metal particles.

In a modification (not shown) of the FIG. 17 embodiment, a uniformlydistributed first selection of cells is blocked with the metal bindermatrix, the cells being wired together and to each other to formemitters. An equal number of cells generally alternating in distributionwith the emitter cells are also blocked with metal binder matrix, thesecond set of cells being wired together and to ground to formcollectors. This arrangement has high efficiency at the surface ofsubstrate cells because the emitter and collector are integral parts ofthe substrate.

In further alternatives, the emitter and collector configurations shownpreviously can be matched differently.

A benefit of induction heating is that converter assemblies can besmaller. A cold start produces 75 to 90% of the pollutants of aninternal combustion engine and this drives the size of the overallexhaust assemblies. Since the induction heating technology addressesmuch of this 75 to 90%, there is the ability to shrink the converterpackage. By introducing added heat and mass transfer with theimplementation of an EHD sub-system, further size reduction is possible.

National emissions standard requirements are a prime driver forcatalytic converter design. The requirements are very high and difficultto meet by with a single converter. Currently, therefore, most cars nowin production employ a two converter assembly—one at a close-coupledposition and the other at an underfloor position. The close-coupledconverter is normally lighter in weight than the underfloor converterwhich means that is has low thermal capacity and so will attain acatalytic reaction operating temperature as quickly as possible.However, the close-coupled converter is of relatively lower efficiencycompared with the heavier underfloor converter once the two convertershave reached their respective catalytic reaction operating temperatures.By introducing induction heating to the exhaust process at start-up, itmay be manufacturers can return to a single converter installation andmeet emission standards by eliminating the need for the close-coupledconverter.

Although embodiments of the disclosure have been described in thecontext of ceramic catalytic converter substrates, stainless steelsubstrates can also be used, with induction heating being implemented ina similar way to that described above. Substrates made of 400 seriesmagnetic alloys can exhibit significant magnetic hysteresis. With asurrounding coil, the outer annular regions of small diameter stainlesssteel substrates heat up extremely quickly owing to their small thermalcapacity.

In the case of EHD heat and mass transfer, in an alternative embodimentof the disclosure using a stainless steel substrate, the catalyticconverter has two steel bricks with the first functioning as an emitterand the second as a collector. In such cases, insertion of wire insertsor injection and curing of metal mastic threads are obviated because thesteel bricks themselves function to emit and collect the free electrons.

Embodiments of the EHD heat and mass transfer disclosure have beendescribed in the context of ferrous alloys such as steel which arecommercially available in common shapes and sizes, and at reasonablecost. Alternative metals may be used for the EHD electrodes providedthat they can survive high temperature reached in the catalyticconverter and repeated temperature cycling as the metal elements in theconverter substrate body move repeatedly from a cold start to operatingtemperature and back again. Generally, alloying gives advantageousmechanical and physical properties such as corrosion/oxidationresistance, high temperature stability, elastic deformation, andformability.

In applying the induction heating and EHD mass and heat transferdisclosures to the structure and operation of a catalytic converter, theelectrical circuit and electrical inputs required to implement inductionheating are different from the are electrical circuit and electricalinputs required to implement EHD heat and mass transfer. In thisrespect, it is likely that the EHD effect is influenced by the appliedinduction field. This could be a positive influence with the inductionfield adding a zigzag component to the electron flow resulting inenhanced heat and mass transfer. Alternatively, the induction field mayeclipse the EHD effect.

The induction heating process and the EHD mass and heat transfer processmay be applied simultaneously or at separate times during, or in thecase of induction heating, immediately before start-up.

FIG. 18 is a schematic view of a catalytic converter system according toan embodiment of the disclosure. A catalytic converter system 75includes a catalytic converter 60 having a plurality of passages tofacilitate at least one catalytic reaction in an exhaust gas 56 from avehicle engine, generating processed exhaust gas 56′. One or moretemperature sensors 50 are coupled to the catalytic converter 60 togenerate temperature signals indicating at least one temperature of thecatalytic converter. The temperature sensors 50 can be implemented viathermocouples, thermistors or other thermal sensors that mounted on orin the catalytic converter in order to monitor the temperature atdifferent locations on or in the converter or via other temperaturemonitors.

Outputs from the temperature sensors 50 are taken to a controller 52 atwhich the monitored temperature or temperatures are used to control theinduction heating via control of an AC generator such as AC source 64.The controller 52 generates a control signal 58 based on thetemperature(s) indicated by these temperature signals. At least oneelectromagnetic field generator including AC source 64 and coil 20responds to the control signal 58 by generating an electromagnetic fieldto inductively to heat the catalytic converter 60. The AC source 64 can,for example, be a variable AC generator that generates an AC signalhaving a magnitude, duty cycle or power that varies as a function of thecontrol signal 58. In another example, the control signal 58 turns theAC source 64 on and off with a duty cycle that varies as a function ofthe magnitude of the desired level of heating. The AC source cangenerate a signal such as a 50 Hz or 60 Hz signal however mediumfrequency signals in the range 1 kHz-100 kHz and radio frequency signalsin the range of 100 kHz-10 MHz or higher frequencies can likewise beemployed.

Controller 52 can be implemented via a processor such as a standaloneprocessor or a shared processing device such as an engine controlmodule. The controller 52 uses one or more algorithms to control theapplied induction and EHD processes in implementations where theinduction field characteristics or the EHD high voltage characteristicsare selectable to achieve a particular induction heating pattern or EHDeffect. The controller 52 can be mounted independently of the catalyticconverter. For example, the controller 52 can be mounted inside thevehicle where the electronic control circuitry is relatively wellprotected. Alternatively, with a weatherproof casing, the convertercontrol module can be placed in the engine bay close to the battery orunder the vehicle close to the catalytic converter.

Consider an example where the catalytic converter 60 is implemented viaa bolt-in assembly in a vehicle to treat internal combustion engineemissions. Platinum group metals or other catalysts in the wash-coatingwork in combination with heat to treat the majority of pollutants in theexhaust gas. The catalytic treatment can be heavily dependent ontemperature. For the process to be effective, a minimum light-offtemperature of about 300 C may need to be reached and maintained. Theexhaust gas treatment process may rapidly drop in efficiency below thistemperature. In normal engine operation, there are several instanceswhere the temperature of the catalytic converter can be below thisthreshold: cold start, cool down and start-stop hybrid vehicle operationas well as other electric vehicles with internal combustion engines.

In a cold start condition, the engine and exhaust system are at ambienttemperature. In really cold environments, this temperature can be as lowas −30 C on a regular basis in winter. Consequently, it can take severalminutes of engine operation before the engine and catalytic convertersheat up to the required temperature. In fact, there is little to noemissions treatment until the system gets up to the thresholdtemperature, typically referred to as “light-off”. Conventionalcatalytic converters are solely reliant on the engine for heat to raisetheir temperature.

Cool down occurs when the engine and exhaust system start out hot andthen the temperature drops below the threshold point. Excessive idlingafter the engine is hot can produce this effect. A low engine RPM willnot produce enough heat to keep the catalytic converter 60 hot. Thegradual cooling may result in a steady-state temperature that is belowthe light-off temperature. Decelerating from high speed can also producethis effect. The engine RPM drops to close to idling levels because nopower is required and, as in the case of idling, there is not enoughheat generated by vehicle exhaust to keep the catalytic converter 60hot. Also, there is a large amount of convection under the vehicle thatrobs heat from the engine and catalytic converter, thus adding to thecooling rate. The issues with current converter technology is the reasonthat idling bans have been put in place by the law makers and also whystop-and-go traffic can be so polluting.

In start-stop hybrid vehicle operation, the vehicle engine can beautomatically turned-off and restarted during vehicle operation. In mildhybrid vehicles, the vehicle engine is stopped by the engine controlmodule to avoid idling when a vehicle is at rest, such as when a vehicleis stopped in traffic. When the driver removes his/her foot from thebrake and engages the accelerator to resume motion, the engine controlmodule quickly restarts the engine is as little as 350 milliseconds. Inhybrid electric vehicles, the internal combustion engine can beturned-off for more extended periods and used only when necessary tosupplement the operation of one or more electric motors that operate viabattery power. Similar to the cold-start and cool-down conditionspreviously described, the catalytic converter may be at ambienttemperature or otherwise lower than light-off temperature.

The induction heating and EHD heat/mass transfer processes previouslydescribed enhance the performance of the emissions treatment by thecatalytic converter system 75 under normal driving conditions includingcold starts and cool down, etc. and otherwise improve emissionstreatment of exhaust gas 56 by the catalytic converter 60. Controloperations can include, but are not limited to:

-   -   (a) Pre-heat—heat catalytic converter before engine starts;    -   (b) Post-heat—heat catalytic converter following engine start;    -   (c) Hybrid—a combination of pre-heat and post-heat where the        catalytic converter is heated before and after engine start;    -   (d) Thermal Management—typically not associated with cold starts        but maintains the converter temperature above light-off with        rapid cooling; and/or    -   (e) Particulate filter regeneration        For example, once light-off temperature is achieved during        pre-heating, the controller 52 can enter a temperature        maintenance mode where the temperature is simply maintained and        not increased. The power demand in the maintenance mode is a        fraction of that required for continuous, intense heat-up.        Maintaining the temperature is accomplished either by pulsing        the full induction power on and off, or by modulating the power.        Pulsing is the more simple process in that the system is either        on or off with only a timer control being required. The        frequency and duration of pulses and the delay between pulses        are selected so that the temperature is maintained constant        within a few degrees. Modulating the power is more complex as        the power output is automatically adjusted with the objective of        maintaining a constant temperature. The more complex induction        circuit needs to be operable through a full range of outputs        from 0% or near zero (say min 20%) on through 100%. In one        embodiment, a maintenance mode is triggered upon cooling of the        catalytic converter while the engine is still running; for        example, in response to cooling when the vehicle engine is        idling. A pulsed or modulated operation similar to those        outlined above is used to prevent excessive cool down.

In a control method according to an embodiment, the temperature sensors50 include one or more thermocouples embedded on the surface of thecatalyst substrate at some point along its length such as at theconverter mid-point. The thermocouple(s) provide direct feedback to thecontroller 52 with no calculation or inference being required.Calibration is first performed to compensate for offset between theoutside and inside of the catalyst substrate. At steady state, thegreatest heat losses from the catalytic converter 60 are at itsperiphery with convection from driving, with rainwater, snow and icecontributing to the losses. During preheating, the perimeter, core, orentire substrate is heated to light-off temperature with compensationbeing made for the calculated offset in temperature between thelight-off temperature of the desired region relative to the temperaturesensor(s) 50.

While described above in conjunction with the use of separatetemperature sensors 50, in addition or in the alternative, thecontroller 52 can use the coil 20 itself for temperature tracking. Inparticular, inductance of the coil 20 changes with increasingtemperature as molecular vibration from heat interferes with themagnetic field. Colder temperatures produce less interference thanhotter temperatures. This interference can be characterized and, fromit, a bulk temperature can be determined by the controller 52. Thesubstrate is the most massive component of the induction system and heatcontained within the substrate has the greatest influence on inductance.The monitored temperature in this method is an average temperature asthe presence of hot and cold spots is not detected. Use of the inductioncoil method obviates the need for an extra wire to the catalyticconverter.

Although control methods and apparatus have been described in thecontext of induction heating, similar control methods and apparatus arealso applied to control electrohydrodynamic (EHD) heat and masstransfer. It should be noted that controller 52 can be configured togenerate the control signals 58 and 66 to operate the induction heatingand EHD processes independently—together or at separate times.

In one example, the induction heating process is implemented beforeengine start-up, for a short time after start up, during idling andduring deceleration. The controller 52 is configured to generate controlsignal 66 to switch on the EHD process only when the engine is runningbecause the process depends on the flow of exhaust gas through theconverter. In this example, the EHD process is run at any time thatthere is flow of exhaust gas through the converter. In another example,the same or similar induction heating program is adopted but EHD processis switched off at a temperature above light-off.

While the battery 62 is shown as providing power to the EHD process, itshould be noted that a battery such as a vehicle battery or othervehicle power system can be used to selectively power the othercomponents of the catalytic converter system 75. In other examples, analternative power source such as a solar cell, external plug in vehiclepower such as provided in conjunction with a block heater or hybridvehicle plug in system can also be used to power the components of thecatalytic converter system 75 in circumstances where alternative poweris available. In operation, the induction heating and EHD processes canbe selectively enabled or disabled under control of the controller 52.In various embodiments, induction heating can be initiated by thecontroller 52 in response to conditions such as: key in the ignition,key strike to run position; key strike to start position, proximity ofthe key within X feet of vehicle, initiation of a remote start function,plug-in vehicle to grid, block heater plug-in, etc. The operations ofcontroller 52 can be disabled in response to light-off temperatureachieved, battery state of charge too low, battery reserve required forstarter reached, manual shut-off of the system, shut-off of the engine,etc.

In should be noted that the vehicle engine can operate via one or moreof the following fuel types including gasoline, diesel, propane,ethanol, natural gas, etc. The control methodologies can be applied tovehicle operating configurations including fulltime conventionalinternal combustion, hybrid—series, parallel, mild parallel,series-parallel or power-split, plug-in hybrid electric, mild hybridauto start-stop, range extended, constant RPM engines, variable RPMengines, or other configurations. The vehicle engine can be normallyaspirated, turbo-charged, super-charged, gas-direct-injected,electronic-fuel-injected, operate via a distributor or othertechnologies.

The catalytic converter 60 can operate via platinum, palladium, rhodiumor other catalyst and can include a diesel oxidation catalyst,particulate filter and/or urea injection system. The substrate caninclude ceramic honeycomb, woven metal, a porous membrane or othersubstrate. The catalytic converter system can be directed to reducingexhaust emissions such as hydrocarbons, carbon monoxide, carbon dioxide,oxides of nitrogen, sulphur dioxide, particulate matter and/or otheremissions to a full range of air-fuel ratios (lambda) such asstoichiometric, rich-burn, lean-burn and/or other ratios.

Further examples regarding the catalytic converter system 75, includingseveral optional functions and features, are presented in conjunctionwith FIGS. 19-22 that follow.

FIG. 19 is a block diagram representation of a feedback control loopaccording to an embodiment of the disclosure. In particular a feedbackcontrol loop 100 is presented where heating of a catalytic converter,such as induction heating of the catalytic converter 60 presented inconjunction with FIG. 18, is represented by a transfer function G(s),the control signal 58 is represented by the signal E(s), a control inputis represented by the signal X(s), and the temperature of the catalyticconverter is represented by signal Y(s), The operation of the controllerand temperature sensor, such as controller 52 and temperature sensor 50,are represented by the feedback function H(s), the generation of controlinput X(s) and summing junction 102. Because the heating and convectivecooling of the catalytic converter can also be impacted by thetemperature and volume of exhaust gases and the speed of the vehicle,these additional factors are represented by the disturbance input D(s)at summing junction 104. Each of these signals quantities arerepresented in the Laplace transform domain via the Laplace transformvariable, s.

The output temperature Y(s) can be calculated as follows:Y(s)=G(s)[X(s)−Y(s)H(s)]+D(s)Or,Y(s)=D(s)+X(s)[G(s)/[1+G(s)/H(s)]]

Consider an example where the transfer function G(s) is modelled as afirst-order system as follows:G(s)=a/(s+ω)And further, a cold start condition where D(s)=T_(am), the feedbackfunction H(s)=k, corresponding to simple proportional control. In thiscase,Y(s)=T _(am) +X(s)[a/(s+ω+ka)]

Considering further that the ambient temperature is T_(am), thecontroller seeks to use induction heating to maintain a referencetemperature T_(ref), and the control input is initiated via a stepfunction at a time t₀=0 with a magnitude kT_(ref). Then the temperatureof the catalytic converter in the time domain y(t) can be found from theinverse Laplace transform as:X(s)=kT _(ref) /sY(s)=T _(am) +kT _(ref) a/[s(s+ω+ka)]y(t)=

⁻¹[Y(s)]=T _(am)+(T _(am))(1−e ^(−t/τ))where τ=1/(ω+ka). In this case, the value of the control signal in thetime domain e(t) for times t>0 is simply:e(t)=k[T _(ref) −y(t)]It should be noted that the value of e(t) may be limited by thefollowing inequality:0≤e(t)≤e _(max)Where e_(mass) represents the maximum output of the AC source 64. Notethat, in most implementations, the induction heating capability does notextend to active cooling—with cooling of the catalytic converterhappening normally via thermal radiation and convection. Thereforenegative values of the e(t) may not be permitted.

An example of operation of such a feedback control loop is presented inconjunction with FIG. 20. While the foregoing has assumed a first-ordermodel for the transfer function G(s), other higher order models withmultiple poles and zeros can likewise be employed, based on the actualtransfer function of the induction heating system and catalyticconverter that are implemented. In addition, while a feedback functioncorresponding to proportional control has been described above, othermore advanced feedback functions implementing proportional, integral,derivative control, and/or more other feedback functions with multiplepoles and zeros can likewise be employed. In addition, while aparticular feedback control loop is implemented, other controltechniques such as feed-forward control; state-space control includingoptimal control, model predictive control, linear-quadratic-Gaussiancontrol; adaptive control; hierarchical control; intelligent controltechniques using various AI computing approaches like neural networks,Bayesian probability, fuzzy logic, machine learning, evolutionarycomputation and genetic algorithms; robust control; stochastic control;non-linear control and/or other control algorithms.

FIG. 20 presents graphical representations of a control signal andcatalytic converter temperature according to an embodiment of thedisclosure. In particular a graph 110 of the control signal e(t) and agraph 110′ of the temperature of the catalytic converter are plotted inthe time domain in accordance with the example presented in conjunctionwith FIG. 19 in a cold start beginning at time t₀=0. As discussed,y(t)=T _(am)+(T _(ref) −T _(am))(1−e ^(−t/τ))ande(t)=k[T _(ref) −y(t)]

As shown, the temperature y(t) begins at the ambient temperature T_(am).When the control e(t) is applied at t₀=0, the induction heating causesthe catalytic converter temperature to rise and asymptotically approachand hold a reference temperature T_(ref), such as the minimum light-offtemperature required for efficient catalytic conversion. At a time t₁,the temperature of the catalytic converter has reached the T_(ref)within an acceptable tolerance and the vehicle engine can be startedwith emission controls being fully functional. Also, at a time t₁, thecontrol signal e(t) has approached zero because the catalytic convertertemperature has approached its reference temperature and heating is nolonger required.

It should be noted that the graphs 110 and 110′ only reflect theoperation of an example catalytic converter system to a cold startcondition. Once the vehicle engine starts and the vehicle begins tomove, D(s) is no longer simply T_(am). Exhaust gases from the vehicleengine contribute heat and motion of the vehicle increases convectionand heat loss. The controller 52 responds to these changes in conditionsto maintain the temperature of the catalytic converter to a value thatis at or above the reference temperature.

FIG. 21 is a block diagram representation of a controller according toan embodiment of the disclosure. In particular, a controller 120 ispresented that can operate in a catalytic converter system and operateas a substitute for controller 52 presented in conjunction with FIG. 19.Like the controller 52, controller 120 operates to generate the controlsignal 58 for controlling the induction heating of the catalytic andcontrol signal 66 for controlling the EHD process of the catalyticconverter. Instead of operating only based on temperature data 130 fromone or more temperature sensors 50 associated with the catalyticconverter, the controller 120 operates based on a wider range of vehiclecontrol data 125 such as ambient temperature data 132, engine RPM data134 that indicates the rotational velocity of the vehicle engine, brakeactivation data 136, clutch activation data 138, remaining battery lifedata 140, stop-start mode data 142, emissions data 144, engine startdata 146, speed data 148 that indicates the speed of the vehicle,traffic data and vehicle navigation data 150 that indicates the path ofthe vehicle, speed limits, current traffic congestion, stop and goconditions, etc. and optionally other engine control data, vehiclestatus data, and vehicle data such as oxygen sensor voltage, oxygensensor temperature, exhaust gas recirculation temperature, coolanttemperature, vehicle acceleration/deceleration, air-fuel ratio (lambda),ignition position, engine timing, exhaust manifold temperature, etc.

In various embodiments, the controller 120 includes a processor and amemory that stores a look-up table (LUT) 122 that responds to the statesof the vehicle indicated by the vehicle control data 125 and generatescontrol signals 58 and 66 that corresponds to the current states. Forexample, the LUT 122 can store control data in accordance with astate-space control algorithm based on vehicle states such as catalyticconverter temperature, ambient temperature, vehicle RPM, vehicle speedindicated by temperature data 130, ambient temperature data 132, RPMdata 134, and vehicle speed data 148. In this fashion, the temperatureof the catalytic converter can be controlled based on changes in exhaustvolume caused by variations in vehicle engine RPM, changes in ambienttemperature, and heat loss due to convection at different vehiclespeeds.

In addition, the controller 120 compares the temperature data 130 withthe reference temperature, such as the light-off temperature of thecatalytic converter. The controller 120 generates an at-temperatureindication signal 152 that indicates when the temperature of thecatalytic converter has reached or is being maintained at or above thereference temperature. This at-temperature indication signal 152 can beused to trigger at-temperature indicator 160, such as a dashboard light,pop-up message on a dash board screen or other user interface thatindicates to the driver of the vehicle when the catalytic converter hasreached or is being maintained at or above the reference temperature, orthat it is ok to start the vehicle. The at-temperature indication signal152 can also be used to trigger vehicle start lock-out 170 as part ofthe vehicle ignition system that enables the vehicle engine to bestarted only when the catalytic converter has reached or is beingmaintained at or above the reference temperature.

Most vehicles now being manufactured are equipped with a wirelesscommunication device in the form of a keyless remote which typicallyincludes door lock, door unlock, trunk release, panic alarm, and,occasionally, remote start capabilities. Smartphone technology is likelyto replace the keyless remote at some point in the future and is alreadyused by some manufactures to enable remote start features via asmartphone application (“app”). In one embodiment, control of catalyticconverter preheating is incorporated into a wireless control device suchas those mentioned previously. In particular, an induction preheatingstart procedure is initiated as part of a remote start procedure, theconverter preheat procedure being initiated at a fixed or selectableperiod of time before the remote engine start is activated. In analternative, the remote wireless control device includes a dedicatedcircuit wherein converter preheating procedure is activatedindependently of any other remote control capability for the vehicle.

With the press of the preheat button or remote start, a vehiclecommunication system receives a wireless communication signal that isused to generate start data 146. In response, the controller 120generates control signal 58 to begin control of the inductively heatedcatalytic converter system. Warming the catalytic converter either tothe light-off temperature or to a temperature close to the light-offtemperature before the vehicle is started, produces less pollutants ingaseous emissions when an engine is cold started. Using a wirelessremote obviates the driver from needing to be in the vehicle in order toperform the preheating procedure because many consumers may not toleratea delay in the normal start-up procedure. In this way, the driver canget into the vehicle, switch on the ignition to start the vehicle, andthen drive away using a hot converter. As an alternative to thisprocedure, the driver enters the vehicle and turns or presses theignition key which generates the start data 146. However, in this case,a delay can be automatically instituted between the time that theignition key is pressed and the time at which the ignition circuit isenergized. During the period of this delay, the controller 120 initiatesthe converter preheating procedure. When the vehicle engine is started,the controller 120 can respond by generating control signal 66 to enablethe EHD process to achieve further efficiency.

Other vehicle control data 125 can be used by controller 120 to generatethe control signals 58 and 66 and/or to adapt the operation ofcontroller 120 to differing vehicle states and conditions. Currentconverter technology uses pre-converter and post-converter oxygensensors to calculate the effective catalytic converter temperature withthe discrepancy between the sensors providing a measure of the convertertemperature. Emissions data 144 generated by these oxygen sensors orfrom other emissions sensors of the vehicle can be used by controller120. For example, when no difference is detected in the emissions data144 between input and output oxygen sensors, the catalyst is not workingso the temperature is below light-off (300 C). Above 300 C, thedifference between the sensors grows and the calculated temperatureincreases proportionately with oxygen conversion. This emissions data144 can be used to supplement the temperature data 130, detecttemperature sensor failure etc.

As previously discussed, in mild hybrid vehicles and electric hybridvehicles, the vehicle engine can be automatically turned-off andrestarted during vehicle operation. Extended stoppage of the vehicleengine during operation can cause the catalytic converter to cool belowthe minimum light-off temperature and increase vehicle emissions. Invarious embodiments, the controller 120 can be adapted to autostart-stop operation. In particular, start-stop mode data 142 canindicate whether auto start-stop functionality is enabled or disabled onvehicles that include this functionality. When auto start-stopfunctionality is enabled, the RPM data 134 can indicate whether theengine is started or stopped. Brake data 136, clutch data 138 andvehicle speed data 148 can further indicate to controller 120 when anauto stop may be imminent. In an embodiment, the controller 120 respondsto starting and stopping of the vehicle engine by generating controldata 66 to start and stop the EHD process in a synchronous fashion. Inaddition, the controller 120 can generate control data 52 to maintainthe temperature of the catalytic converter when the engine is stopped,preventing a cold start condition when the engine is subsequentlyrestarted.

In a further embodiment, the controller 120 includes a drive modeprediction generator 124 analyzes the vehicle control data 125 in orderto predict a current driving mode from a set of possible driving modessuch as:

-   -   (a) a non-hybrid stop-and-go traffic mode characterized by        continuous vehicle engine operation, frequent an/or extended        stops accompanied by idling    -   (b) a highway mode characterized by continuous vehicle engine        operation, high vehicle speeds, limited braking and clutch        operation, moderate RPM and high rates of convection;    -   (c) an extended idle mode where the vehicle is running but        stopped for an extended length of time;    -   (d) an auto start-stop stop-and-go traffic mode characterized by        frequent an/or extended stops accompanied by auto start-stop;    -   (e) an electric-only mode of a hybrid vehicle where the vehicle        engine is stopped and is may not be started until the        electric-only mode is exited;    -   (f) hybrid electric mode where the vehicle engine may be stopped        for extended periods and restarted only when required, etc.        The controller adaptively generates the control signal 58 in        accordance with the current driving modes. In non-hybrid        stop-and-go traffic mode, extended idle mode or highway mode,        the controller 120 can generate the control signals 58 as        previously discussed to trigger induction heating, only as        required to maintain the temperature of the catalytic converter        at or above the light-off temperature. In auto start-stop        stop-and-go traffic mode, the controller 120, for shorter stops,        can generate the control signals 58 as previously discussed to        trigger induction heating, only as required to maintain the        temperature of the catalytic converter at or above the light-off        temperature. For longer stops that can be predicted based on a        pattern caused by stop and go commuter traffic or traffic light        stops, based on traffic data and navigation 150, or based on        other driving patterns, the controller 120 may allow the        temperature of the catalytic converter to fall below the        light-off temperature for short periods as long as the        controller predicts that reheating to light-off temperature can        be initiated and completed before the controller 120 predicts        that a restart will occur. For example, the controller 120 can        operate to control the catalytic converter temperature to a        standby temperature that is lower than the light-off        temperature. The standby temperature can be selected to save        power, but be close enough to the light-off temperature so as to        minimize the reheating time required to return the catalytic        converter temperature to light-off for vehicle engine restart.        While the foregoing has considered particular driving modes, the        controller 120 can also predict and adapt to other driving modes        such as aggressive driving, timid driving, hypermiling, etc.

Likewise, in hybrid electric mode, the controller may allow thetemperature of the catalytic converter to fall below the light-offtemperature as long as the controller predicts that reheating tolight-off temperature can be initiated and completed before thecontroller 120 predicts that a restart will occur. In an embodimentauto-start data from the engine control module may indicate based onvehicle speed, navigation route guidance, traffic conditions, that arestart of the engine is imminent and may initiate heating from thecurrent temperature or from a standby temperature to light-offtemperature, as required, for completion before the controller 120predicts that a restart will occur. Further in electric-only mode of ahybrid vehicle, the controller may pre-heat the catalytic converter onlywhen electric only mode is exited or when the controller 120 predictsthat a restart of the vehicle engine will occur.

Converter preheating power can be, as previously discussed, providedfrom an on-board battery. Car batteries can supply heating power onlyfor a short period of time depending on the power draw. Preheating withthe vehicle engine off may be more limited due to lower battery voltageswhen compared with cases where the car engine is running and aconsistent 14 VDC is available from the car battery. Diesel cars andtrucks typically have larger batteries than regular gas cars owing tothe use of glow plugs which must be preheated in order to facilitate thecombustion process. Diesel vehicles generally have more availableonboard electrical power than conventional cars. Hybrid electricvehicles have large amounts of battery capacity, however they rely onthis capacity to enhance vehicle range and lower the cost of operation.

In an embodiment, the controller 120 generates the control signals 58and 66 in accordance with a low power mode when the remaining charge inthe battery compares unfavorably with a low power threshold. Thecatalytic converter heating is initiated by controller 120 andmaintained for as long as possible commensurate with maintainingsufficient battery power to start the car. The power level of thebattery is monitored prior to and during the converter preheatingprocedure and battery life data 140 indicating the remaining batterylife is used by the controller 120 to enter a low power mode. In thislow power mode, for example, the controller can disable the inductionheating and EHD processes from the onset or stop the induction heatingand/or EHD processes when the remaining battery life is, or falls belowa minimum reliable power threshold indicating that further use couldcompromise a vehicle start or other vehicle operation.

Converter preheating power can optionally be provided from the utilitygrid. The use of grid power is current practice for range-extendedhybrid, plug-in hybrid, block-heater, and electric vehicles. The car isplugged in either at a standard receptacle or a vehicle-specificreceptacle. Block-heaters are typically used in cold climates especiallywith diesel engines. Plugging in the block-heater keeps the enginecoolant warmed to enable easier starts and to prevent coolant fromfreezing. Grid power is used both to maintain batteries in a fullycharged condition and also to prepare the battery pack for driving use.Batteries do not operate well in conditions of extreme cold or extremeheat and battery packs providing a climate control system are used tomaintain the battery temperature at a moderate temperature enablingmaximum power.

For example, grid power from a garage or public place receptacle can beused inductively to preheat the catalytic converter of internalcombustion vehicles. In this approach there is no limitation on heat-upperiod as compared to running directly off the onboard battery. Of note,grid power is one-fifth the cost of gasoline for the same energyproduced and because a vehicle will often be at its home location orwith access to a public receptacle, preheating using grid can be usedfor most cold start conditions. To activate, in one variation, thekeyless entry, smartphone or other wireless command is used to preheatthe converter for a predetermined period before the driver gets in anddrives away. In an alternative, the keyless remote feature is used topreheat the catalyst for a predetermined time before the car isautomatically started. This ensures that the emissions are as clean aspossible upon start-up and while still allowing the consumer to have theremote start feature. Inductively heating the converter is onlyperformed until the light-off temperature is achieved because there islittle to no benefit in exceeding the light-off temperature.

In various embodiments, the controller 120 is coupled to communicatewith a connected car interface 175 of the vehicle that provides featuressuch as vehicle Internet access, wireless connectivity between thevehicle and wireless user devices such as a smartphone, tablet,smartwatch, laptop computer or other computing device, as well aswireless access for use in service and vehicle diagnostics, vehicleinspections and other connectivity. Emissions data 144 received from anengine control module or from separate emission sensors can be processedand/or stored in a memory associated with the controller 120 in order toprovide a historical record of actual vehicle emissions.

This historical emissions data can be retrieved via the connected carinterface 175 and provided to a user smartphone, tablet, home computeror other user device for the purposes of maintaining a record of vehicleemissions. In addition, the historical emissions data can be provided aspart of a vehicle inspection that requires a test of not only currentemissions, but also of historical emissions data. Further, thehistorical emissions data can be provided to service personnel to use invehicle diagnostics and repair.

The data indicating actual vehicle emissions can be used for otherpurposes. For example, the connected car interface 175 can provide thisdata to an in-dash display, user smart phone or tablet or other displayscreen as part of an application or utility that presents a display ofcurrent emissions to the occupants of the vehicle during a trip. In asimilar fashion, control data 58 and 66 indicating the activation of theinduction heating and/or EHDC processes can be provided to the connectedcar interface 175 and indicated on the display, letting the occupants ofthe vehicle know that, for example, these systems are operating toreduce emissions. The application or utility can optionally provide acomparison of actual emissions to theoretical emissions had theinduction heating and/or EHDC processes not been in operation anddisplay to the vehicle occupants the benefits, in terms of reducedemissions, provided by these systems. In a further example, dataindicating the maintenance of low emissions goals by the vehicle can bereported via the connected car interface 175 and used to qualify thevehicle owner for tax credits, high occupancy vehicle status, rewards orother incentives.

FIG. 22 is a flow diagram representation of a method according to anembodiment of the disclosure. In particular, a method is presented foruse in conjunction with one or more functions and features presented inconjunction with FIGS. 1-21. Step 200 includes generating a temperaturesignal indicating a temperature of a catalytic converter. Step 202includes generating a control signal based on the temperature signal.Step 204 includes generating an electromagnetic field to inductively toheat the catalytic converter in response to the control signal.

In various embodiments, the control signal is generated further based ona reference temperature, to control the temperature of the catalyticconverter in accordance with the reference temperature. The method canfurther include generating an at temperature signal indication signalwhen the at least one temperature of the catalytic converter comparesfavorably to the reference temperature. Start-up of a vehicle engine canbe enabled in response the at temperature signal indication signal.

In various embodiments, the controller generates the control signalfurther based on at least one of: a signal indicating a rotationalvelocity of the vehicle engine; a signal indicating an ambienttemperature of the vehicle containing the catalytic converter system; asignal indicating an auto start-stop mode of the vehicle engine; asignal indicating a remaining charge in a vehicle battery. The methodcan further include predicting a current one of a plurality of drivingmodes based on vehicle control data and the control signal can begenerated in accordance with the current one of the plurality of drivingmodes. The method can further include controlling an electrohydrodynamicheat/mass transfer process of the catalytic converter system.

FIG. 23 is a block diagram representation of an electromagnetic fieldgenerator 300 according to an embodiment of the disclosure. Inparticular, a magnetic field generator 300 is presented that includesthe AC source 64 and metal coil 20. In operation, the AC source respondsto a control signal, such as control signal 58, by generating a magneticfield 310 to inductively heat a catalytic converter substrate, such assubstrate 10. In particular, the magnetic field generator 300 includes acoil, such as metal coil 20, that radiates the magnetic field 310.

A potential issue with operating AC source 64 from a battery, such as avehicle battery, is that there is a correlation between the voltagedraw, current draw, and therefore power draw. This can cause powervariations during preheat of the emission control device. The batterymay be fully charged so that the voltage is relatively high, forinstance when the alternator of a vehicle just finished charging thebattery before the vehicle was turned off. A high voltage results in ahigh current draw and thus a high power. In other cases, the batterycharge may be depleted so that the battery voltage is relatively low,for instance when there has been excessive draw on the battery when theengine was not running. This can happen when the interior lights orother accessories are on for an extended period of time. A low voltageresults in a low current and thus a low power. Furthermore, the batteryvoltage may not be constant within a given engine start cycle. Thevoltage will go down with the start when the battery power is drawn downand then back up when the alternator kicks in to charge the battery. Thedrop in battery voltage at the start can be as low as 11 VDC andalternator can charge as high as 13.5 VDC or more. This difference canbe as much as 20%. Based on the correlation between voltage and current,this means that the current can be different by as much as 20% too. Thelow voltage draw of 80% and the low current draw of 80% produce a powerdraw just after start of 64% (80% Vdraw×80% A=64% W) of the power drawat the end of the cycle. This 36% swing in power between the start andend of the heating cycle can result in lost heating opportunity andefficiency and a longer heating time to reach light-off temperature ofthe emission control device.

In operation, the control signal 58 is generated by the controller 52 or120 to control induction heating of the emission control device. Thecontrol signal 58 can include an indication to initiate heating of theemission control device at start-up of an engine that contains theemission control device or a predetermined time thereafter (e.g. 1 sec,2 secs, 5 seconds, 10 seconds, 20 seconds, etc). In addition to theindication to initiate heating, the control signal 58 can also indicatea power set point such as a targeted amount of power transfer or otherpower level.

The control signal 58 can also provide an indication to discontinueinduction heating of the emission control device. For example, thecontroller 52 or 120 can generate the control signal 58 to discontinueinduction heating of the emission control device a predetermined timeafter induction heating of the emission control device is initiated(e.g. an expected amount of time to reach light off temperature such as200 seconds of other time period). In other cases, the controller 52 or120 can generate the control signal 58 based on comparison of atemperature of the emission control device to a reference temperature,such as light-off temperature. As previously discussed, the temperatureof the emission control device can be determined based on a temperaturesensor such as a thermocouple or based on a change in impedance of thecoil. In this fashion, the control signal 58 can be generated toactivate induction heating at temperatures below light-off and todeactivate induction heating when light-off temperature is reached. Thecontroller 52 or 120 can also generate the control signal 58 to suspendinduction heating of the emission control device in response to ano-load condition of the coil indicated, for instance by the presence ofa coil voltage and a low coil current or lack of a coil current.Furthermore, the controller 52 or 120 can monitor a temperature of oneor more components of the electromagnetic field generator 300,particularly the power amplifier 304. The controller 52 or 120 cangenerate the control signal 58 to discontinue induction heating of theemission control device when the temperature exceeds a temperaturethreshold to avoid damage to the components of the power amplifier 304and/or other components of the electromagnetic field generator 300.

The electromagnetic field generator 300 responds to the control signal58 by selectively generating a power signal that is applied to the metalcoil 20 to cause the induction heating of the emission control device.The electromagnetic field generator 300 operates, for example, tomaintain a fixed power draw during the voltage draw peaks and valleys byadjusting a frequency of the power signal to control the powertransferred to the coil.

In various embodiments, oscillator 306 such as a voltage controlledoscillator, ring oscillator, or other oscillator circuit is configuredto generate the power signal. In particular, the oscillator operatesunder control of the controller 308 to adjust the frequency of the powersignal to stabilize power transfer. For example, the controller 308 canmonitor a coil current, coil voltage, current draw and/or otheroperational parameters of the AC source 64 and include a look-up table,state machine, or iterative control algorithm in order to select afrequency that improves the power factor, to match a resonant frequencyof a tank circuit that includes the coil or otherwise to stabilize orotherwise improve and/or stabilize the power transferred by the magneticfield generator 300 to the conductive components of the catalyticconverter substrate for improved induction heating.

A power amplifier 304, such as a class A, Class B, Class C, Class D orClass E (including combinations thereof) power amplifier circuit isconfigured to amplify the power signal to generate an amplified powersignal at an output of the power amplifier 304 to drive the coil. Thepower amplifier 304 can include one or more transistors such as bipolarjunction transistors, insulated-gate bipolar transistors, metal oxidesemiconductor field effect transistors (MOSFETs) and/or other powertransistors. In various embodiments, the power amplifier 304 operates asa switch to generate an AC power signal at its output.

An impedance matching network 302 is configured to impedance match theoutput of the power amplifier 304 to the coil. In particular, theimpedance matching network 302 can include one or more capacitors toform a resonant tank circuit with the coil, such as metal coil 20 andoptionally one or more other reactive impedances such as capacitorsand/or inductors in a Pi-network, L-network or other impedance matchingcircuit configuration. In various embodiments, controller 308 isconfigured to adjust an impedance of the impedance matching network toimprove power transfer. For example, the controller 308 can monitor acoil current, coil voltage, current draw, power signal frequency and/orother operational parameters of the AC source 64 and include a look-uptable, state machine, or iterative control algorithm in order to controlan adjustable impedance to improve the power factor, to match theimpedance of a tank circuit that includes the coil or otherwise tomaximize or otherwise improve the power transferred by the magneticfield generator 300 to the conductive components of the catalyticconverter substrate for improved induction heating.

The electromagnetic field generator 300 optionally includes a back-uppower supply 305 that includes a capacitor, rechargeable battery orother rechargeable storage device that is charged by the vehicle duringperiods when the electromagnetic field generator 300 is not operating orexcess power from the vehicle is otherwise available. In circumstanceswhere the operation of the system is inconsistent/intermittent due tohigh loads on the vehicle power supply system, the back-up power supply305 provides supplemental power to the electromagnetic field generator300 to enable uninterrupted operation of the control and inductionsystem, such as control to its specified/target output level.

Consider the following example, the oscillator 306 generates one or moreswitching signals such as a square wave with substantially a 50% dutycycle (e.g., 45%-55%). The power amplifier 304, in turn, supplies a highvoltage/high current version power signal by switching between 0 VDC anda higher voltage. In various embodiments, the power amplifier 304 isimplemented a via an H-switching insulated gate bipolar transistorcircuit that is controlled by two square wave signals with substantially50% duty cycle signals of different phases and the same frequencygenerated by the oscillator 306. The switching signals have a“dead-time” during switching in which neither signal is high. Thisallows the switching elements in the H-switching insulated gate bipolartransistor circuit to switch off completely before the next element isturned on. This prevents “shoot-through”, a condition in which a shortcircuit is created when both switching elements are on or partially on.

The controller 308 controls the power transferred to the metal coil 20by adjusting the frequency of the power signal. The resonant frequencyof the metal coil 20 is given by:

$\begin{matrix}{F_{RES} = \frac{1}{2\pi\sqrt{2{LC}}}} & (1)\end{matrix}$

Where: F_(RES) is the resonant frequency of the metal coil (in Hz).

-   -   L is the inductance of the metal coil 20 (in Henrys).

C is the capacitance of a resonant capacitance of the impedance matchingnetwork 302 (in Farads).

Maximum power is transferred to the metal coil 20 at its resonantfrequency. As the frequency is increased above resonance the powertransferred to the metal coil 20 drops. In various embodiments, thecontroller 308 monitors a voltage and/or current of the power signal andadjusts the frequency of the power signal based on the voltage of thepower signal to control the power transferred to the coil that istransferred to the metal coil 20. In particular, the frequency of thepower signal can be dynamically selected, based on the coil voltage todraw a current with a constant power draw that, after an initializationperiod for example, matches the desired power set point. This can beaccomplished by monitoring the coil voltage and/or current via voltageor current sensors and using controller 308 to make empiricaladjustments to the power signal frequency. This allows the magneticfield generator 300 to operate during quiescent periods at the samepower at 11 volts on through 13.5 volts and also adapt to changes inmaterial properties due to temperature. As the emission control devicerises in temperature, the induction coil resistance and heating wireinductance will change. Tuning adjustments in the frequency of the powersignal can ensure that temperature does not adversely impact the powerdraw.

In various embodiments, the controller 308 determines the powertransferred to the metal coil 20, compares the power transferred to thecoil to the power set point and selects the frequency of the powersignal based on a comparison of the power transferred to the coil andthe power set point. The controller 308 can select the frequency of thepower signal by:

-   -   (a) decreasing the frequency of the power signal when the power        transferred to the metal coil 20 is below the power set point;        and    -   (b) increasing the frequency of the power signal when the power        transferred to the coil is above the power set point.        For example, the frequency of the power signal can be adjusted        between a maximum frequency limit and a minimum frequency limit.        The maximum frequency limit can be set to a predetermined        frequency above the resonant frequency of the metal coil 20,        such as 150% of the resonant frequency, 200% of the resonant        frequency or some other value. The minimum frequency limit can        be set at the resonant frequency of the metal coil 20.

The resonant frequency of the coil can vary based on ambient conditionsand also vary based on changes in the inductance of the metal coil 20during operation. In various embodiments, the controller 20 candetermine the initial resonant frequency of the coil via a measurementprocedure. In addition, the controller 20 can determine changes in theresonant frequency of the coil by repeating the measurement procedure.For example, the controller 20 can run a frequency sweep of the powersignal or operate via another iterative measurement procedure todetermine F_(RES) as the frequency were the power transfer peaks. Forexample, the measurement procedure can be run at engine startup, re-runperiodically during the run-up to the desired temperature setpointand/or at times when the induction heating would otherwise be shut off,such as during time period when the temperature setpoint has beenreached. Further examples are presented in conjunction with FIGS. 28 and29.

In various embodiments, the controller 308 can initiate inductionheating by starting the power signal at a high frequency, such as themaximum frequency limit and ramp down to the heating frequency in apredetermined amount of time, such as 2 seconds, 5 seconds, 10 secondsor some other time. This prevents high initial current surges or voltagespikes to the metal coil 20 during turn on. Once at the heatingfrequency, the power output is maintained for the heating period andthen the power signal is turned off.

In various embodiments, the frequency of the power signal can beselected by the controller 308 in discrete frequency steps of differentsizes such as large frequency steps and small frequency steps that aresmaller than the large frequency steps. For example, when there is achange in power set point, the frequency of the power signal can beadjusted in large frequency steps until the new power set point isreached. When there is no change in the power set point, the frequencyof the power signal can be adjusted in small frequency steps in order tomaintain the power transfer at or near the power set-point. An examplealgorithm is presented below:

-   -   1. If operating power set point changed, set step size to large.    -   2. Measure operating power level.    -   3. If at power set point then do not change frequency. If less        than set point then decrease frequency by step size otherwise,        increase frequency by step size. Do not exceed the maximum or        minimum frequency limits.    -   4. Measure new operating power level.    -   5. If step size set to large:        -   a. If the set point has not been reached or overshot go to            step 3.        -   b. Otherwise, the set point has been reached or overshot.            Set the step size to small and go to step 3.

In another mode of operation, once the resonant frequency is determinedfor a set of operating conditions corresponding to maximum powertransfer, the power can be regulated by the controller 308 to a lowerpower set point by using the resonant frequency, but by pulsing thepower on for certain pulse durations over a time period (e.g. 100 msec,500 msec, 1 sec, 2 seconds or some greater or lesser time period) andoff the remaining portions of that time period. The average power cancorrespond to the desired power setpoint but the induction draw will begreater than the power setpoint for the power-on portion of the timeperiod and zero for the remaining portion of the time period. If theresonant frequency of the metal coil 20 changes, for example, due tochanges in coil inductance, the controller 308 can periodicallydetermine the new resonant frequency by running a frequency sweep orother iterative measurement procedure and determining the resonantfrequency as the frequency with maximum power transfer to the coil.Using the resonant frequency can generate greater thermal and electricalefficiency. The average of the peak and off (zero power) periodsproduces the overall desired heating/power. If, for example, the desiredpower set point is 90% of the maximum power, the resonant frequency canbe applied to the metal coil 20 with a 90% duty cycle—90% of the timethe power signal is applied to the coil and the coil can be turned-offthe other 10% of the time. In addition, the regulation of both thefrequency and the pulse durations can be applied to the control of thepower transfer to the metal coil 20.

While the foregoing control methodologies have focused primarily onvehicle systems and 50% duty cycles, in some applications includingmining or industrial applications, higher duty cycles can be applied toheating of the emission control device. While the controller 308 isshown as being separate from controllers 52 and 120, it should be notedthat the functionality of controller 308 can likewise be incorporated ineither of the other control devices for implementation via a singleprocessor, circuit or other device.

While not expressly shown, the controller 52 or 120 and/or othercontroller can be coupled to a memory for storing operating parametersand/or to a display such as a vehicle display or monitor for use indiagnostics and/or review by the operator of the vehicle or other systemthat contains the emission control device. Operating parameters such astemperature, voltage, current, resonant frequency, time to light-off,and other operating conditions as well as error conditions and otherdata can be stored, displayed and/or output, for example, as graphicsand/or a text file, csv file or other data file. Normal operation can beindicated and error messages can be generated to ensure the safety ofthe operator, the vehicle and the induction heating system. Realtimevoltage, current, frequency and power can be stored and displayed alongwith the temperature of the emission control device. The results of aconnection safety check can be stored and displayed indicating there isa load and coil attached before the initiation of induction heating or afault if no load is found. The temperature of the power amplifier 304can be displayed and/or indications of normal operating temperature andan over-temperature fault.

While the foregoing has focused on the measurement of resonant frequencyfor use in control of induction heating of the emission control system,changes in resonant frequency can be used for other purposes as well.Values of the resonant frequency can be stored over time and used tomonitor and indicate life cycle degradation of the emission controlsystem. Furthermore, the resonant frequency can be compared to a highand/or low life cycle threshold frequencies. If the measured resonantfrequency exceeds either of these boundaries, the controller 52 or 120or other controller can generate an indication that the maximum lifespanof the emission control system has been reached. In response, theinduction heating system can be deactivated by the controller 52 or 120or other controller and/or a corresponding fault indication can bedisplayed.

In another example, resonant frequency can be used to detect the Curietemperature of the pins or the magnetic saturation limit of either thepins or the magnetic flux concentrator and used as a trigger todeactivate the induction heating to avoid a runaway condition or othersystem instability caused by drastic load changes. The rate of change ofthe resonant frequency can be tracked as induction heating is activatedand compared to a rate of change threshold. Up to the curie temperatureor saturation limits, the rate of change of the resonant frequency isrelatively constant with time and thus somewhat predictable. Uponreaching the curie point or saturation limits, the rate of change of theresonant frequency increases drastically. Detecting an increase of therate of change of the resonant frequency above the rate of changethreshold and controlling the power transfer below this threshold canensure maximum power delivery, maximum efficiency, and thus maximumheating.

FIG. 24 is a block diagram representation of an electromagnetic fieldgenerator 300 according to an embodiment of the disclosure. Inparticular, a magnetic field generator 300 is presented that includesmany common functions and features described in conjunction with FIG. 23that are referred to by common reference numerals. In the embodimentshown however, the magnetic field generator 300 includes a plurality ofcoils, such as metal coils 20 and separate drive paths 350, 352, etc.

The controller 308 operates to control the operation of each of themetal coils 20 in response to one or more control signals 58. Inaddition to the functions and features described in conjunction withFIG. 23, the controller 308 operates in response to the control signal58 to selectively enable and disable the separate drive paths 350, 352,etc. in order to activate selected ones of the plurality of coils.Consider the case where the control signal 58 commands the AC source 64to produce only a fraction of the maximum power at a particular time. Inthis case, one or more of the coils can be deactivated by disablingtheir corresponding drive path(s) in order to produce more fine control.Because the coils, when driven, modify the inductance of one anotherbased on changes in mutual inductance, activating and deactivating thevarious coils can be accompanied by adjustments to the one or moreimpedances of the corresponding matching circuit(s) 302 and/oradjustments to the frequency of the corresponding oscillator(s) 306 ofthe activated drive paths in order to improve the power factor, adjustthe resonant frequency of a tank circuit that includes the coil, adjustthe resonant frequency of the coil to match the drive frequency orotherwise to maximize or otherwise improve the power transferred by themagnetic field generator 300 to the conductive components of theemission control device for improved induction heating.

FIG. 25 is a graphical diagram 400 of a control set point as a functionof time according to an embodiment of the disclosure. In particular acontrol set point 402 is shown that, for example, is included in controlsignal 58. The control set point 402 can be used to control theoperation of a magnetic field generator, such as the magnetic fieldgenerator 300 presented in conjunction with FIGS. 23-24 or otherinduction heating element of an emission control device associated withan engine.

At time t₀, the engine associated with the emission control device isstarted. The control set point 402 implements a start delay beforeactivating the induction heating of the coil and setting the initialpower set point P₁ at time t₁. The start delay allows electromagneticfield generator 300 to be initialized and allows the battery voltage topotentially stabilize before the coil is commanded to turn on. Asdiscussed in conjunction with FIG. 23, the electromagnetic fieldgenerator 300 operates by adjusting a frequency of the power signal inorder to reach and maintain the power transferred to the coil at thepower set point P₁.

At time t₂, the induction heating of the coil is deactivated and thepower set point 402 is reset to zero, either because the temperature isdetermined to have reached light-off or an error condition has beendetected such as a no-load coil condition or power amplifierover-temperature condition or because a predetermined initial timeperiod has expired. At time t₃, the induction heating of the coil isreactivated, the power set point 402 is set to a lower value P₂, inabsence of error conditions, for example, because the temperature isdetermined to have fallen below light-off or otherwise to maintain thetemperature of the emission control device at or above light-off. Attime t₄ the induction heating of the coil is deactivated again and thepower set point 402 is reset to zero. While, in the example shown, thereis a delay between t₃ and t₂, the lower power program with power setpoint P₂ can be set to begin immediately after the initial program attime t₂.

While the power set point 402 is shown as having two discrete values, inother embodiments a greater or fewer number of values could be used.Furthermore, the timing presented is for illustrative purposes only andis not necessarily drawn to scale.

FIG. 26 is a graphical diagram 410 of a power signal as a function oftime according to an embodiment of the disclosure. In particular, thepower signal 412 at the coil, such as metal coil 20, is shown. Asdiscussed in conjunction with FIG. 23, the power signal 412 is a squarewave, however other wave forms can be likewise be employed.

The period of the power signal is T_(i) and the frequency (in Hz) is1/T_(i). As previously discussed, the frequency of the power signal 412can be controlled and or the power signal 412 can be pulsed on and off acontrolled percentage of time (e.g with a controlled duty cycle) inorder to control the power transfer to the metal coil 20.

FIG. 27 is a flow diagram 420 of a method according to an embodiment ofthe disclosure. In particular, a method is presented for use with one ormore functions and features discussed in conjunction with FIGS. 1-26.Step 422 includes generating a control signal to initiate inductionheating of an emission control device. Step 424 includes generating, inresponse to the control signal a power signal, wherein the power signalis applied to a coil to cause the induction heating of the emissioncontrol device. Step 424 includes adjusting a frequency of the powersignal, to control a power transferred to the coil.

FIG. 28 is a flow diagram 440 of a method according to an embodiment ofthe disclosure. In particular, a method is presented for use with one ormore functions and features discussed in conjunction with FIGS. 1-26.Step 442 includes determining, via a controller such as controller 308or other controller, a resonant frequency of a coil, such as metal coil20. Step 444 includes selecting, via the controller, a frequency of apower signal based on the resonant frequency of the coil. Step 446includes generating, via the controller, a control signal to controlinduction heating of an emission control device. Step 446 includesgenerating, via an alternating current (AC) source (such as AC source 64or other AC source) and responsive to the control signal, a power signalapplied to the coil in proximity to the emission control device to causethe induction heating of the emission control device.

In various embodiments, the controller determines the resonant frequencyof the coil by iteratively adjusting the frequency of the power signal.For example, the controller can iteratively adjust the frequency of thepower signal in discrete frequency steps between a minimum frequency anda maximum frequency. The controller can operate to iteratively adjustthe frequency of the power signal in discrete frequency steps to aplurality of candidate frequencies, measure an amount of powertransferred to the coil at the plurality of candidate frequencies anddetermine the resonant frequency of the coil by selecting one of thecandidate frequencies corresponding to a peak in the amount of powertransferred to the coil. The controller can operate to update theresonant frequency of the coil to compensate for changes in aninductance of the coil and/or select the frequency of the power signalto be above the resonant frequency of the coil. The controller canoperate to select the frequency of the power signal to be the resonantfrequency of the coil and control an amount of power transferred to thecoil by controlling a duty cycle of the AC source.

In various embodiments, the control signal indicates a power set point,and the AC source determines a power transferred to the coil, comparesthe power transferred to the coil to the power set point and selects thefrequency of the power signal further based on a comparison of the powertransferred to the coil and the power set point. The frequency of thepower signal can be selected from a candidate frequency between amaximum frequency limit and a minimum frequency limit. The maximumfrequency limit can be selected to be above the resonant frequency ofthe coil and/or the minimum frequency limit can be determined based onthe resonant frequency of the coil.

FIG. 29 is a flow diagram 460 of a method according to an embodiment ofthe disclosure. In particular, a method for determining the currentresonant frequency of a coil is presented for use with one or morefunctions and features discussed in conjunction with FIGS. 1-28. Thefollowing parameters are used:

-   -   Fres0, the previously calculated value of the coil resonant        frequency or a default value if the resonant frequency has not        been previously calculated.    -   Fmin, the minimum candidate frequency for the resonant frequency    -   Fmax, the maximum candidate frequency for the resonant frequency    -   Fstep, the frequency step size between adjacent candidate        frequencies    -   Pthres, the power threshold indicating measurably significant        differences in power    -   F1, the current candidate frequency    -   F2, the next candidate frequency    -   Fdir, frequency search direction (either +1 or −1)    -   P1, power transfer to the coil at F1    -   P2, power transfer to the coil at F2        In various embodiments, Fstep=a fixed frequency such as 25 Hz,        50 Hz, 100 Hz, 250 Hz or other fixed frequency. Fmin=18 KHz and        Fmax=22 KHz however other frequencies can be employed based on        the capacitance C and the possible inductance of the coil L.        Pthres=a fixed power differential such as 10 W, 25 W, 50 W or        100 W, however greater or lesser values can be used based on the        measurement accuracy, the desired efficiency, and the maximum        power transfer.

In Step 462, F1 is set to Fres0, Fdir is set to +1, F2 is set toF1+(Fdir*Fstep) and F2 is clipped to Fmin if it would be otherwise lessthan Fmin or to Fmax if it would otherwise be greater than Fmax. In step464, P1 and P2 are measured. In step 466, the method determines if theabsolute magnitude of P2-P1 exceeds Pthres. If not, the method proceedsto step 468 to determine if F2 is either at Fmin or Fmax. If not, themethod proceeds to step 470 where F2 is set to F2+(Fdir*Fstep), and F2is clipped to Fmin if it would be otherwise less than Fmin or to Fmax ifit would otherwise be greater than Fmax and the method proceeds back tostep 464. If F2 is neither Fmin or Fmax, the method proceeds to step474. If however, the absolute magnitude of P2-P1 exceeds Pthres in step466, the method proceeds to step 472. In step 472, the method determinesif P2 is greater than P1. If not, the method also proceeds to step 474where the Fdir is set to −Fdir, i.e. the direction of search isreversed. In step 478, the method determines if Fdir is +1. If not themethod proceeds to step 480 where F2 is set to F1+(Fdir*Fstep) and F2 isclipped to Fmin if it would be otherwise less than Fmin or to Fmax if itwould otherwise be greater than Fmax, and further proceeds back to step464. Otherwise, step 478 proceeds to step 482 where the Fres is set asF1. If P2 is greater than P1, the method proceeds directly to step 480and on to step 464.

While a particular algorithm for determining the current resonantfrequency is presented, other iterative measurement procedures could beemployed. For example, an exhaustive search algorithm could be performedwhere the power transfer to the coil is measured at all candidatefrequencies between Fmax and Fmin (at discrete intervals with a stepsize of Fstep)—with the resonant frequency chosen as the candidatefrequency with the highest power transfer. Other search algorithms couldlikewise be employed including gradient search algorithms with adaptivestep size, a Fibonacci search algorithm, a Bayesian search algorithm, agenetic search or other optimization algorithm that determines thefrequency that maximizes the power transfer to the coil.

As previously discussed, the resonant frequency measurement procedurecan be run at engine startup, re-run periodically during the run-up tothe desired temperature setpoint and/or at times when the inductionheating would otherwise be deactivated—such as during time period whenthe temperature setpoint has been reached or exceeded, down times whenthe induction heating is in pulsed control and is off and/or other timeswhen the induction system is not running. During these periods, theresonant frequency measurement procedure can be run at very low powerlevels with minimal induction heating effects and very low power drainwhen compared with the power used during normal induction heating.

Consider the case where the temperature of the emission control deviceis determined based on a change in impedance of the coil indicated by achange in resonant frequency. Measured temperatures after light offtemperature has been reached and induction heating has been deactivatedcan be used by the controller 52, 120 or 308 to detect cooling of theemission control system and be used as a basis for reactivating theinduction heating. Furthermore, temperatures measured in this fashioncan be used by the engine controller for other purposes.

FIG. 30 is a graphical diagram 500 of a temperature hysteresis curveaccording to an embodiment of the disclosure. As previously discussed,the temperature of the emission control device—and more particularly,the temperature of the substrate can be used to control the inductionheating. Furthermore, the temperature of the emission control device canbe determined based on a change in impedance of the coil.

In various embodiments, a controller such as controller 52, 120 or 308operates by determining a resonant frequency of a coil, such as metalcoil 20 or other coil, and generating a control signal, such as controlsignal 58 or other control signal, to control induction heating of theemission control device via the coil. An alternating current (AC)source, such as AC source 64 or other AC source, responds to the controlsignal by selectively generating a power signal to the coil tofacilitate the induction heating of the emission control device via thecoil. In various embodiments, generating the control signal can include:determining a temperature of the emission control device based on atemperature hysteresis curve and the resonant frequency of the coil; andgenerating the control signal to command the AC source to generate thecontrol signal to selectively activate and deactivate induction heatingby comparing the temperature of the emission control device to one ormore temperature thresholds.

An example temperature hysteresis curve 502 is presented that indicatesthe relationship between temperature of the substrate of the emissioncontrol device and the inductance of the coil. The temperaturehysteresis curve 502 includes a first portion 506 below the midline 504corresponding to when the induction heating of the emission controldevice is activated and a second portion 508 above the midline 504corresponding to when the induction heating of the emission controldevice is deactivated. When induction heating is activated, thetemperature of the substrate and pins is largely a function of theinduction heating. When the induction heating is deactivated, thetemperature of the substrate and pins is more a function engine RPM andthe heating and/or cooling caused by the temperature of the exhaustgasses. This temperature hysteresis effect can be used, for example, bythe controller to apply different frequency tuning for inductionheating—based on where the starting point is on the hysteresis curve ata given power level.

The temperature hysteresis curve 502 shown provides correction for thesedifferences by differing temperature/inductance relationships for thesetwo different states. Consider the following example. The resonantfrequency, F_(res) is measured. The inductance of the coil is determinedasL=1/(8Cπ ² F _(res) ²)=L1The temperature of the substrate, T is determined as

T=T1, if the induction heating is activated

T=T2, if the induction heating is deactivated

In this fashion, the temperature of the ceramic substrate can beapproximately measured and a control signal can be generated to initiateinduction heating at temperatures below light-off and to discontinueheating when light-off temperature is reached or exceeded.

While a particular temperature hysteresis curve is presented as afunction of inductance and whether or not induction heating isactivated, functions of other or additional variables such as engineRPM, ambient temperature, emissions data 144 generated by oxygen sensorsor from other emissions sensors of the vehicle, other vehicle controldata 125 and/or other parameters from engine operations or other vehiclesensors can likewise be employed to increase the accuracy of thetemperature measurement. In this case, a look-up table can store amulti-dimensional database of temperature measurements indexed by notonly resonant frequency and on/off induction heating state but one ormore of these other parameters as well. Furthermore, while the foregoinghas discussed the conversion between coil inductance and resonancefrequency, in other embodiments the temperature hysteresis curve can bedirectly represented as a function of resonance frequency of the coil.In addition, while the temperature hysteresis curve is presentedgraphically, the temperature hysteresis curve can be implemented in acontroller, such as controller 52, 120 or 308, as a look-up table, statemachine or control algorithm.

FIG. 31 is a flow diagram 520 of a method according to an embodiment ofthe disclosure. In particular, a method for determining the currentresonant frequency of a coil is presented for use with one or morefunctions and features discussed in conjunction with FIGS. 1-30. Step522 includes determining, via a controller, a resonant frequency of acoil. Step 524 includes generating, via the controller, a control signalto control induction heating of an emission control device based on theresonant frequency of the coil. Step 526 includes selectivelygenerating, via an alternating current (AC) source and responsive to thecontrol signal, a power signal to the coil to facilitate the inductionheating of the emission control device via the coil.

In various embodiments, generating the control signal includes:determining a temperature of the emission control device based on atemperature hysteresis curve and the resonant frequency of the coil; andgenerating the control signal to command the AC source to generate thecontrol signal when the temperature of the emission control device isbelow a temperature threshold. Determining the temperature of theemission control device can include: determining an inductance of thecoil based on the resonant frequency of the coil; and wherein thetemperature hysteresis curve includes a first portion that correlatesthe inductance of the coil to the temperature of the emission controldevice when the induction heating of the coil is activated and a secondportion that correlates the inductance of the coil to the temperature ofthe emission control device when the induction heating of the coil isdeactivated.

In various embodiments, the temperature hysteresis curve can include afirst portion corresponding to when the induction heating of theemission control device is activated and a second portion correspondingto when the induction heating of the emission control device isdeactivated. The control signal can indicate an on-state of the ACsource or an off-state of the AC source. The AC source can respond tothe on-state of the control signal by activating the induction heatingof the emission control device via the coil and respond to the off-stateof the control signal deactivating the induction heating of the emissioncontrol device via the coil.

In various embodiments, the controller determines the resonant frequencyof the coil by iteratively adjusting a frequency of the power signal.For example, the controller iteratively adjusts the frequency of thepower signal in discrete frequency steps between a minimum frequency anda maximum frequency. In a further example, the controller iterativelyadjusts the frequency of the power signal in discrete frequency steps toa plurality of candidate frequencies, measures an amount of powertransferred to the coil at the plurality of candidate frequencies anddetermines the resonant frequency of the coil by selecting one of thecandidate frequencies corresponding to a peak in the amount of powertransferred to the coil.

FIG. 32 is a graphical diagram 530 of a temperature, inductance andresonance characteristic according to an embodiment of the disclosure.In particular, a further example is presented that shows therelationship between the resonant frequency Fres and inductance L for acoil, such as metal 20, that is measured as induction heating progressesfrom ambient temperature to a temperature of 500° C. In comparison tothe diagram of FIG. 30, the inductance L is presented for a portion ofthe temperature hysteresis curve corresponding to the system state whenthe induction heating of the emission control device is activated. Asshown, the resonant frequency F_(res) decreases with induction heatingto higher temperatures, while the inductance L increases.

As may be used herein, the terms “substantially” and “approximately”provides an industry-accepted tolerance for its corresponding termand/or relativity between items. Such an industry-accepted toleranceranges from less than one percent to fifty percent and corresponds to,but is not limited to, component values, integrated circuit processvariations, temperature variations, rise and fall times, and/or thermalnoise. Such relativity between items ranges from a difference of a fewpercent to magnitude differences. As may also be used herein, theterm(s) “configured to”, “operably coupled to”, “coupled to”, and/or“coupling” includes direct coupling between items and/or indirectcoupling between items via an intervening item (e.g., an item includes,but is not limited to, a component, an element, a circuit, and/or amodule) where, for an example of indirect coupling, the intervening itemdoes not modify the information of a signal but may adjust its currentlevel, voltage level, and/or power level. As may further be used herein,inferred coupling (i.e., where one element is coupled to another elementby inference) includes direct and indirect coupling between two items inthe same manner as “coupled to”. As may even further be used herein, theterm “configured to”, “operable to”, “coupled to”, or “operably coupledto” indicates that an item includes one or more of power connections,input(s), output(s), etc., to perform, when activated, one or more itscorresponding functions and may further include inferred coupling to oneor more other items. As may still further be used herein, the term“associated with”, includes direct and/or indirect coupling of separateitems and/or one item being embedded within another item.

As may be used herein, the term “compares favorably”, indicates that acomparison between two or more items, signals, etc., provides a desiredrelationship. For example, when the desired relationship is that signal1 has a greater magnitude than signal 2, a favorable comparison may beachieved when the magnitude of signal 1 is greater than that of signal 2or when the magnitude of signal 2 is less than that of signal 1. As maybe used herein, the term “compares unfavorably”, indicates that acomparison between two or more items, signals, etc., fails to providethe desired relationship.

As may also be used herein, the terms “processing module”, “processingcircuit”, “processor”, and/or “processing unit” may be a singleprocessing device or a plurality of processing devices. Such aprocessing device may be a microprocessor, micro-controller, digitalsignal processor, microcomputer, central processing unit, fieldprogrammable gate array, programmable logic device, state machine, logiccircuitry, analog circuitry, digital circuitry, and/or any device thatmanipulates signals (analog and/or digital) based on hard coding of thecircuitry and/or operational instructions. The processing module,module, processing circuit, and/or processing unit may be, or furtherinclude, memory and/or an integrated memory element, which may be asingle memory device, a plurality of memory devices, and/or embeddedcircuitry of another processing module, module, processing circuit,and/or processing unit. Such a memory device may be a read-only memory,random access memory, volatile memory, non-volatile memory, staticmemory, dynamic memory, flash memory, cache memory, and/or any devicethat stores digital information. Note that if the processing module,module, processing circuit, and/or processing unit includes more thanone processing device, the processing devices may be centrally located(e.g., directly coupled together via a wired and/or wireless busstructure) or may be distributedly located (e.g., cloud computing viaindirect coupling via a local area network and/or a wide area network).Further note that if the processing module, module, processing circuit,and/or processing unit implements one or more of its functions via astate machine, analog circuitry, digital circuitry, and/or logiccircuitry, the memory and/or memory element storing the correspondingoperational instructions may be embedded within, or external to, thecircuitry comprising the state machine, analog circuitry, digitalcircuitry, and/or logic circuitry. Still further note that, the memoryelement may store, and the processing module, module, processingcircuit, and/or processing unit executes, hard coded and/or operationalinstructions corresponding to at least some of the steps and/orfunctions illustrated in one or more of the Figures. Such a memorydevice or memory element can be included in an article of manufacture.

One or more embodiments have been described above with the aid of methodsteps illustrating the performance of specified functions andrelationships thereof. The boundaries and sequence of these functionalbuilding blocks and method steps have been arbitrarily defined hereinfor convenience of description. Alternate boundaries and sequences canbe defined so long as the specified functions and relationships areappropriately performed. Any such alternate boundaries or sequences arethus within the scope and spirit of the claims. Further, the boundariesof these functional building blocks have been arbitrarily defined forconvenience of description. Alternate boundaries could be defined aslong as the certain significant functions are appropriately performed.Similarly, flow diagram blocks may also have been arbitrarily definedherein to illustrate certain significant functionality.

To the extent used, the flow diagram block boundaries and sequence couldhave been defined otherwise and still perform the certain significantfunctionality. Such alternate definitions of both functional buildingblocks and flow diagram blocks and sequences are thus within the scopeand spirit of the claims. One of average skill in the art will alsorecognize that the functional building blocks, and other illustrativeblocks, modules and components herein, can be implemented as illustratedor by discrete components, application specific integrated circuits,processors executing appropriate software and the like or anycombination thereof.

In addition, a flow diagram may include a “start” and/or “continue”indication. The “start” and “continue” indications reflect that thesteps presented can optionally be incorporated in or otherwise used inconjunction with other routines. In this context, “start” indicates thebeginning of the first step presented and may be preceded by otheractivities not specifically shown. Further, the “continue” indicationreflects that the steps presented may be performed multiple times and/ormay be succeeded by other activities not specifically shown. Further,while a flow diagram indicates a particular ordering of steps, otherorderings are likewise possible provided that the principles ofcausality are maintained.

The one or more embodiments are used herein to illustrate one or moreaspects, one or more features, one or more concepts, and/or one or moreexamples. A physical embodiment of an apparatus, an article ofmanufacture, a machine, and/or of a process may include one or more ofthe aspects, features, concepts, examples, etc. described with referenceto one or more of the embodiments discussed herein. Further, from figureto figure, the embodiments may incorporate the same or similarly namedfunctions, steps, modules, etc. that may use the same or differentreference numbers and, as such, the functions, steps, modules, etc. maybe the same or similar functions, steps, modules, etc. or differentones.

Unless specifically stated to the contrary, signals to, from, and/orbetween elements in a figure of any of the figures presented herein maybe analog or digital, continuous time or discrete time, and single-endedor differential. For instance, if a signal path is shown as asingle-ended path, it also represents a differential signal path.Similarly, if a signal path is shown as a differential path, it alsorepresents a single-ended signal path. While one or more particulararchitectures are described herein, other architectures can likewise beimplemented that use one or more data buses not expressly shown, directconnectivity between elements, and/or indirect coupling between otherelements as recognized by one of average skill in the art.

The term “module” is used in the description of one or more of theembodiments. A module implements one or more functions via a device suchas a processor or other processing device or other hardware that mayinclude or operate in association with a memory that stores operationalinstructions. A module may operate independently and/or in conjunctionwith software and/or firmware. As also used herein, a module may containone or more sub-modules, each of which may be one or more modules.

While particular combinations of various functions and features of theone or more embodiments have been expressly described herein, othercombinations of these features and functions are likewise possible. Thepresent disclosure is not limited by the particular examples disclosedherein and expressly incorporates these other combinations.

What is claimed is:
 1. An emission control system comprising: anemission control device having a plurality of passages to facilitateemission control of an exhaust gas from a vehicle engine; a controllerthat operates by: determining a resonant frequency of a coil; andgenerating a control signal to control induction heating of the emissioncontrol device based on the resonant frequency of the coil, whereingenerating the control signal includes determining a temperature of theemission control device based on a temperature hysteresis curve and theresonant frequency of the coil, and wherein the temperature hysteresiscurve has a first temperature value and a second temperature value for avalue of the resonant frequency of the coil; and an alternating current(AC) source that responds to the control signal by selectivelygenerating a power signal to the coil to facilitate the inductionheating of the emission control device via the coil.
 2. The emissioncontrol device of claim 1 wherein the temperature of the emissioncontrol device is determined to be the first temperature for the valueof the resonant frequency of the coil when the induction heating of thecoil is activated and the temperature of the emission control device isdetermined to be the second temperature for the value of the resonantfrequency of the coil when the induction heating of the coil isdeactivated, and wherein generating the control signal further includes:generating the control signal to command the AC source to generate thecontrol signal when the temperature of the emission control device isbelow a temperature threshold.
 3. The emission control system of claim 2wherein determining the temperature of the emission control deviceincludes: determining an inductance of the coil based on the resonantfrequency of the coil; and wherein the temperature hysteresis curveincludes a first portion that correlates the inductance of the coil tothe temperature of the emission control device when the inductionheating of the coil is activated and a second portion that correlatesthe inductance of the coil to the temperature of the emission controldevice when the induction heating of the coil is deactivated.
 4. Theemission control device of claim 2 wherein the temperature hysteresiscurve includes a first portion corresponding to when the inductionheating of the emission control device is activated and a second portioncorresponding to when the induction heating of the emission controldevice is deactivated.
 5. The emission control device of claim 1 whereinthe control signal indicates an on-state of the AC source or anoff-state of the AC source.
 6. The emission control device of claim 5wherein the AC source responds to the on-state of the control signal byactivating the induction heating of the emission control device via thecoil.
 7. The emission control device of claim 5 wherein the AC sourceresponds to the off-state of the control signal deactivating theinduction heating of the emission control device via the coil.
 8. Theemission control system of claim 1 wherein the controller determines theresonant frequency of the coil by iteratively adjusting a frequency ofthe power signal.
 9. The emission control system of claim 8 wherein thecontroller iteratively adjusts the frequency of the power signal indiscrete frequency steps between a minimum frequency and a maximumfrequency.
 10. The emission control system of claim 8 wherein thecontroller iteratively adjusts the frequency of the power signal indiscrete frequency steps to a plurality of candidate frequencies,measures an amount of power transferred to the coil at the plurality ofcandidate frequencies and determines the resonant frequency of the coilby selecting one of the candidate frequencies corresponding to a peak inthe amount of power transferred to the coil.
 11. A method comprising:determining, via a controller, a resonant frequency of a coil;generating, via the controller, a control signal to control inductionheating of an emission control device based on the resonant frequency ofthe coil, wherein generating the control signal includes determining atemperature of the emission control device based on a temperaturehysteresis curve and the resonant frequency of the coil, and wherein thetemperature hysteresis curve has a first temperature value and a secondtemperature value for a value of the resonant frequency of the coil; andselectively generating, via an alternating current (AC) source andresponsive to the control signal, a power signal to the coil tofacilitate the induction heating of the emission control device via thecoil.
 12. The method of claim 11 wherein the temperature of the emissioncontrol device is determined to be the first temperature for the valueof the resonant frequency of the coil when the induction heating of thecoil is activated and the temperature of the emission control device isdetermined to be the second temperature for the value of the resonantfrequency of the coil when the induction heating of the coil isdeactivated, and wherein generating the control signal further includes:generating the control signal to command the AC source to generate thecontrol signal when the temperature of the emission control device isbelow a temperature threshold.
 13. The method of claim 12 whereindetermining the temperature of the emission control device includes:determining an inductance of the coil based on the resonant frequency ofthe coil; and wherein the temperature hysteresis curve includes a firstportion that correlates the inductance of the coil to the temperature ofthe emission control device when the induction heating of the coil isactivated and a second portion that correlates the inductance of thecoil to the temperature of the emission control device when theinduction heating of the coil is deactivated.
 14. The method of claim 12wherein the temperature hysteresis curve includes a first portioncorresponding to when the induction heating of the emission controldevice is activated and a second portion corresponding to when theinduction heating of the emission control device is deactivated.
 15. Themethod of claim 11 wherein the control signal indicates an on-state ofthe AC source or an off-state of the AC source.
 16. The method of claim15 wherein the AC source responds to the on-state of the control signalby activating the induction heating of the emission control device viathe coil.
 17. The method of claim 16 wherein the AC source responds tothe off-state of the control signal deactivating the induction heatingof the emission control device via the coil.
 18. The method of claim 11wherein the controller determines the resonant frequency of the coil byiteratively adjusting a frequency of the power signal.
 19. The method ofclaim 18 wherein the controller iteratively adjusts the frequency of thepower signal in discrete frequency steps between a minimum frequency anda maximum frequency.
 20. The method of claim 18 wherein the controlleriteratively adjusts the frequency of the power signal in discretefrequency steps to a plurality of candidate frequencies, measures anamount of power transferred to the coil at the plurality of candidatefrequencies and determines the resonant frequency of the coil byselecting one of the candidate frequencies corresponding to a peak inthe amount of power transferred to the coil.